The CIA secretly aids Ukraine in countering Putin by providing funding, equipment, and training to an elite Ukrainian commando unit, known as Unit 2245. This assistance, initiated in 2016, aims to reverse-engineer Russian drones and communications equipment, as well as to break Moscow’s encryption systems.

Located amidst a thick woodland, the Ukrainian military base seems to have been devastated and left for dead, with its command center reduced to a charred shell after being hit by Russian missiles at the beginning of the conflict.

However, that is above ground.

A short distance away, a covert tunnel leads to an underground bunker where units of Ukrainian soldiers follow Russian spy satellites and listen in on talks between Russian generals. A red line on one screen traced the path of an explosive drone from a site in central Ukraine to a target in the Russian city of Rostov, weaving through Russian air defenses.

Ukrainian intelligence has revealed that Maxim Kuzminov, a Russian pilot who defected to Ukraine, was shot dead in Spain.

The underground bunker serves as the military’s covert nerve center and was constructed to replace the command center that was destroyed in the months following Russia’s invasion.

One other secret is that the C.I.A. provides practically all of the base’s funding and equipment.

Top intelligence commander Gen. Serhii Dvoretskiy stated in an interview at the base, “One hundred and ten percent.”

As the third year of a conflict that has claimed hundreds of thousands of lives approaches, Washington and Kiev’s intelligence cooperation is essential to Ukraine’s self-defense. The CIA and other U.S. intelligence organizations follow the movements of Russian troops, maintain espionage networks, and give intelligence for targeted missile strikes.

However, the alliance was not formed during a conflict, and Ukraine is not the only gainer.

It began a decade ago, gaining traction under three very different American presidents in fits and turns, propelled by influential people who frequently performed risky actions. It has made Ukraine—whose intelligence services were long thought to be seriously infiltrated by Russia—one of Washington’s most significant intelligence allies in the current war against the Kremlin.

The listening station in the Ukrainian forest is a component of a network of spy bases built over the last eight years, along the Russian border, with backing from the C.I.A. The network consists of twelve covert locations. Prior to the conflict, the Ukrainians demonstrated their worth to the Americans by gathering intelligence that demonstrated Russia’s complicity in the downing of Malaysia Airlines Flight 17, a commercial aircraft, in 2014. The Russian agents who interfered in the 2016 U.S. presidential election were pursued by the Americans with assistance from the Ukrainians.

In order for C.I.A. technicians to reverse-engineer Russian drones and communications equipment and break Moscow’s encryption systems, the C.I.A. started training an elite Ukrainian commando unit, known as Unit 2245, in 2016. (Kyrylo Budanov, the current general, was one of the unit’s officers.

Additionally, the C.I.A. assisted in the training of a new generation of Ukrainian spies who worked in Cuba and other areas where the Russians have a significant presence, as well as inside Russia and throughout Europe.

The relationship is so strong that in the weeks leading up to Russia’s invasion in February 2022, C.I.A. officials stayed in a distant location in western Ukraine when the Biden administration evacuated U.S. soldiers. The officers provided vital intelligence during the invasion, such as the locations of Russia’s strike plans and the weaponry they intended to employ.

“Without them, there would have been no way for us to resist the Russians, or to beat them,” said Ivan Bakanov, who was then head of Ukraine’s domestic intelligence agency, the S.B.U.

For ten years, the specifics of this intelligence collaboration have been kept under wraps; nevertheless, The New York Times is now revealing many of these details for the first time.

In over two centuries of interviews, officials from the United States, Europe, and Ukraine, both current and former, portrayed a partnership that almost collapsed due to mistrust before it grew steadily and made Ukraine into an intelligence hub that intercepted more Russian communications than the C.I.A. station in Kyiv could initially process. Many of the officials discussed intelligence and delicate diplomatic topics while speaking under anonymity.

With Russia on the attack and Ukraine increasingly relying on sabotage and long-range missile strikes that need spies well behind enemy lines, these intelligence networks are now more crucial than ever. And they are getting more and more vulnerable: the C.I.A. might have to make cuts if Republicans in Congress decide to stop providing military aid to Kyiv.

William J. Burns, the director of the Central Intelligence Agency, paid his tenth covert visit to Ukraine since the invasion last Thursday in an attempt to reassure Ukrainian leaders.

President Vladimir V. Putin of Russia served as the initial common enemy that united the C.I.A. and its Ukrainian allies. Mr. Putin, who was obsessed with “losing” Ukraine to the West, had been meddling in the country’s politics on a regular basis. He had chosen leaders he thought would keep Ukraine in Russia’s sphere of influence, but each time it backfired, forcing demonstrators into the streets.

Mr. Putin has long held the Western intelligence services responsible for inciting anti-Russian sentiment in Ukraine and influencing Kyiv.

A top European official claims that in late 2021, while Mr. Putin was debating whether to go ahead with his full-scale invasion, he met with the chief of one of Russia’s main spy services. The spy chief informed him that the C.I.A. and Britain’s MI6 were in charge of Ukraine and were using it as a base of operations against Moscow.

However, the Times research revealed that a crucial dynamic was misunderstood by Mr. Putin and his advisors. The C.I.A. refrained from invading Ukraine. Because they were worried about upsetting the Kremlin and believed that Ukrainian leaders could not be trusted, U.S. officials were frequently hesitant to fully engage.

However, a small group of Ukrainian intelligence officers diligently courted the C.I.A. and over time became indispensable to the Americans. During a meeting with the deputy station chief of the C.I.A. in 2015, Gen. Valeriy Kondratiuk, the head of military intelligence for Ukraine at the time, abruptly handed over a stack of top-secret files.

Secrets concerning the Russian Navy’s Northern Fleet, including comprehensive knowledge of the most recent Russian nuclear submarine designs, were included in that first batch. Before long, teams of C.I.A. agents were routinely checking out from his office, their backpacks brimming with paperwork.

“We understood that we needed to create the conditions of trust,” General Kondratiuk said.

The Ukrainians staged killings and other deadly operations in violation of the terms the White House believed the Ukrainians had agreed to, as their frustration with what they perceived as Washington’s excessive caution grew after 2016. Washington officials were furious and vowed to stop supporting, but they never followed through.

“The relationships only got stronger and stronger because both sides saw value in it, and the U.S. Embassy in Kyiv — our station there, the operation out of Ukraine — became the best source of information, signals and everything else, on Russia,” said a former senior American official. “We couldn’t get enough of it.”

This is the unsung tale of how everything came to pass.

A Cautious Beginning

Eight years to the day before Russia launched its full-scale invasion of Ukraine, on February 24, 2014, two phone conversations set the stage for the C.I.A.’s cooperation in that country.

The pro-Kremlin government of Ukraine had just been overthrown by millions of people, and both the president, Viktor Yanukovych, and his espionage chiefs had fled to Russia. A shaky pro-Western government swiftly came to power amid the chaos.

When Valentyn Nalyvaichenko, the government’s new spy chief, arrived at the domestic intelligence agency’s headquarters, he saw a stack of burning documents in the courtyard. Numerous machines were either infected with Russian malware or had been completely erased.

“It was empty. No lights. No leadership. Nobody was there,” Mr. Nalyvaichenko said in an interview.

He walked to an office and made calls to the local head of MI6 and the chief of the C.I.A. station. Even though it was almost midnight, he called them into the office, offered a three-way partnership, and asked for assistance in starting the agency over from scratch. That was the beginning, Mr. Nalyvaichenko stated.

The danger of the situation quickly increased. Putin took control of Crimea. His operatives incited separatist uprisings stirred the east of the nation, which eventually resulted in war. With the country at war, Mr. Nalyvaichenko requested aerial photography and further intelligence from the C.I.A. to aid in the defense of Ukraine’s borders.

As the violence increased, John O. Brennan, the C.I.A. director at the time, boarded an unmarked government aircraft from the United States and landed at a Kyiv airport. According to U.S. and Ukrainian authorities, he informed Mr. Nalyvaichenko that the C.I.A. was interested in forming a relationship, but only at a pace the agency was comfortable with.

How long Mr. Nalyvaichenko and the pro-Western government would last was an unanswered question for the C.I.A. In the past, the C.I.A. was set on fire in Ukraine.

Ukraine won independence in 1991 as the Soviet Union broke up, but it soon found itself divided between opposing political factions who desired to stick close to Moscow and those that preferred to side with the West. Similar cooperation between Mr. Nalyvaichenko and the C.I.A. was initiated during his earlier tenure as espionage head, but it ended when the nation turned back toward Russia.

Mr. Brennan now clarified that the Ukrainians needed to demonstrate their ability to give the Americans intelligence that was valuable in order to be granted access to C.I.A. help. Additionally, they had to get rid of Russian spies since the S.B.U., the country’s spy service, was overrun with them. As one example, the Russians discovered Mr. Brennan’s purportedly covert visit quite fast. The C.I.A. director was shown in a manipulated photograph by the Kremlin’s propaganda channels sporting clown makeup and a wig.)

After Mr. Brennan left, President Barack Obama’s advisors in Washington were quite worried about stirring up trouble in Moscow. Secret regulations crafted by the White House were viewed as handcuffs by some in the C.I.A. and angered the Ukrainians. The regulations prohibited intelligence services from offering Ukraine any assistance that would be “reasonably expected” to result in death.

It was a careful balancing act as a result. The C.I.A. was intended to bolster Ukrainian intelligence services while avoiding escalation with Russia. There was always a continual tension in the collaboration since the red lines were never exactly obvious.

General Kondratiuk, a longstanding adviser to Mr. Nalyvaichenko, was chosen to lead counterintelligence in Kyiv. Together, they established a new paramilitary organization that was stationed behind enemy lines to perform operations and obtain intelligence that the C.I.A. or MI6 would not supply.

This unit, called the Fifth Directorate, would be composed of officers who were born after Ukraine attained independence.

“They had no connection with Russia,” General Kondratiuk said. “They didn’t even know what the Soviet Union was.”

Nearly 300 passengers and crew members were killed when Malaysia Airlines Flight 17, which was traveling from Amsterdam to Kuala Lumpur, blew up in midair and crashed in eastern Ukraine that summer. Within hours of the disaster, the Fifth Directorate obtained telephone intercepts and other intelligence that swiftly established the separatists’ Russian-backed affiliation.

After being pleased, the C.I.A. gave members of the Fifth Directorate and two other elite units specialized training and secure communications equipment, marking its first significant commitment.

“The Ukrainians wanted fish and we, for policy reasons, couldn’t deliver that fish,” said a former U.S. official, referring to intelligence that could help them battle the Russians. “But we were happy to teach them how to fish and deliver fly-fishing equipment.”

A Secret Santa

A loyal collaborator of the C.I.A., Mr. Nalyvaichenko was replaced in the summer of 2015 by an ally, thanks to a coup by Petro Poroshenko, the president of Ukraine. But the adjustment brought about a different opportunity.

Following a reorganization, General Kondratiuk was named director of the nation’s military intelligence organization, the HUR, where he had begun his professional career years before. It would be a pioneering example of how the C.I.A.’s participation in Ukraine would be furthered by personal ties rather than policy changes.

The HUR was authorized, in contrast to the domestic agency, to gather intelligence abroad, notably in Russia. However, because the agency was perceived as a stronghold of Russian loyalists and wasn’t generating any useful intelligence on the Russians, the Americans had little interest in maintaining it.

In an attempt to foster confidence, General Kondratiuk set up a meeting and gave over a bundle of classified Russian documents to his American colleague at the Defense Intelligence Agency. Senior D.I.A. officials, however, disapproved of forging deeper connections and were dubious.

The general had to locate a more cooperative comrade.

Previously, during his tenure at the domestic agency, General Kondratiuk paid a visit to the C.I.A. headquarters located in Langley, Virginia. During those discussions, he got to know a cheerfully bearded C.I.A. agent who had been selected to take over as Kyiv’s next station head.

Following an exhausting day of talks, the C.I.A. brought General Kondratiuk to a Washington Capitals hockey game, where he and the newly hired station chief sat in an opulent box and vociferously jeered at the team’s top Russian player, Alex Ovechkin.

When General Kondratiuk turned over the classified Russian Navy records to the C.I.A., the station chief was still missing. He assured them that there was more where this came from, and the records were forwarded to Langley analysts.

The C.I.A. became General Kondratiuk’s main ally when the analysts determined the documents were genuine and the station chief arrived in Kyiv.

General Kondratiuk was aware that the C.I.A. was necessary to bolster his own organization. The C.I.A. believed the general could potentially assist Langley as well. It found it difficult to enlist spies within Russia due to the intense monitoring of its case officers.

“For a Russian, allowing oneself to be recruited by an American is to commit the absolute, ultimate in treachery and treason,” General Kondratiuk said. “But for a Russian to be recruited by a Ukrainian, it’s just friends talking over a beer.”

The new station chief started going to see General Kondratiuk on a regular basis. In General Kondratiuk’s office, there was an aquarium with a model of a sunken Russian submarine surrounded by yellow and blue fish, which are the national colors of Ukraine. The two men grew close, which fueled the ties between the two agencies, and the new station chief was given a loving moniker by the Ukrainians: Santa Claus.

General Kondratiuk took a plane to Washington in January 2016 to attend meetings at Scattergood, a home on the C.I.A. site in Virginia where the organization frequently hosts distinguished guests. The agency consented to assist the HUR in updating its technology and enhancing its capacity to intercept military communications from Russia. General Kondratiuk promised to give the Americans access to all of the raw intelligence in return.

The collaboration was now genuine.

Operation Goldfish

Today, minefields surround the secret base’s small route, which was planted in the weeks following Russia’s invasion as a defensive measure. The base appeared to be closed when Russian missiles struck it, but the Ukrainians returned a few weeks later.

Under the direction of General Dvoretskiy, teams received funding and supplies from the C.I.A. and started to rebuild—but underground. They only operated at night and when Russian surveillance satellites were not overhead in order to avoid being discovered. Additionally, workers parked their vehicles far from the construction site.

General Dvoretskiy gestured toward massive computer servers and communications equipment inside the bunker, some of which were funded by the C.I.A. He said that his guys were breaking into the secure communications networks of the Russian military utilizing the base.

During a tour, General Dvoretskiy informed a Times journalist, “This is the thing that breaks into satellites and decodes secret conversations,” and said that they were also breaking into surveillance satellites from Belarus and China.

Two newly created maps that demonstrate how Ukraine is monitoring Russian activity worldwide were set on a table by another officer.

The first one displayed the paths taken by Russian spy satellites as they passed over central Ukraine. The second demonstrated how Russian surveillance satellites are flying over important military locations in the eastern and central United States, including a nuclear weapons site.

Following the crucial meeting at Scattergood in 2016, the C.I.A. started supplying encrypted radios and technology for surreptitiously intercepting adversary communications, according to General Dvoretskiy.

Years may sometimes pass before the C.I.A. gains sufficient confidence in a foreign organization to start working together on cooperative operations. It had taken less than six months with the Ukrainians. The new alliance began generating so much unprocessed Russian intelligence that it had to be sent to Langley.

But there were red lines in the C.I.A. It wouldn’t assist the Ukrainians in carrying out their deadly assault operations.

According to a former senior U.S. official, “we made a distinction between intelligence collection operations and things that go boom.”

‘This is Our Country’

The Ukrainians found this distinction to be irritating.

Initially, General Kondratiuk became irritated when the Americans declined to supply satellite photos taken within Russia. Not long after, he asked the C.I.A. for help in organizing a covert mission to send HUR commandos into Russia to detonate explosives against Russian military rail depots. Ukrainians may set off the bombs to stop the Russian forces if they attempted to annex more of their country.

As one former official put it, the superiors “lost their minds” when the station chief told them. To ensure that the mission was canceled and that Ukraine complied with the red lines prohibiting lethal activities, Mr. Brennan, the director of the C.I.A., called General Kondratiuk.

General Kondratiuk canceled the mission, but he also took a different lesson. “Going forward, we worked to not have discussions about these things with your guys,” he said.

An unmanned shoulder-fired rocket launcher was installed in a seized territory building by a group of Ukrainian operatives. It was situated immediately across from the headquarters of Mikhail Tolstykh, also known as Givi, a rebel commander. According to U.S. and Ukrainian officials, they used a remote trigger to fire the launcher as soon as Givi entered his office, killing him.

This was a shadow war gone full throttle. The commander of Ukraine’s elite commando squad, Unit 2245, was killed by the Russians using a car bomb. Col. Maksim Shapoval, the commander, was traveling to Kyiv to meet with C.I.A. officers when his car blew up.

The C.I.A. station commander and U.S. ambassador to Ukraine, Marie Yovanovitch, stood in sadness at the colonel’s wake. Afterwards, C.I.A. agents and their Ukrainian colleagues raised a glass of whiskey to Colonel Shapoval.

“For all of us,” General Kondratiuk said, “it was a blow.”

Tiptoeing Around Trump

The election of Donald Trump in November of 2016 caused anxiety among the Ukrainians and their C.I.A. allies.

Mr. Trump downplayed Russia’s involvement in election meddling while applauding Mr. Putin. Because of his mistrust of Ukraine, he later attempted to get Volodymyr Zelensky, the country’s president, to look into Mr. Biden, his Democratic opponent, which led to Mr. Trump’s first impeachment.

However, Mr. Trump’s administration frequently took the opposite course from what he stated and did. This is due to the fact that Mr. Trump appointed proponents of Russia to important roles, such as Mike Pompeo as director of the C.I.A. and John Bolton as national security adviser. They went to Kyiv to reaffirm their unwavering support for the covert alliance, which grew to encompass the construction of other covert facilities and more specialized training programs.

Because of how well the partnership worked, the C.I.A. sought to establish similar partnerships with other European intelligence agencies that had a similar emphasis on opposing Russia.

The chief of the C.I.A. division in charge of managing operations against Russia, known as Russia House, called a covert meeting at The Hague. There, officials from several agencies, including the C.I.A., the HUR, Britain’s MI6, the Dutch service (a vital ally in intelligence), and others, decided to begin combining more of their information about Russia.

As a result, a covert alliance was formed against Russia, of which the Ukrainians were an essential component.

March to War

The Russian military began amassing soldiers along the Ukrainian border in March 2021. It became unclear as the months went by and more troops surrounded the nation if Mr. Putin was pulling a ploy or getting ready for battle.

The C.I.A. and MI6 sent a single, cohesive message to their Ukrainian allies in November of that year and the weeks that followed: Russia was getting ready for a full-scale invasion with the goal of overthrowing the government and installing a puppet in Kyiv that would carry out the orders of the Kremlin.

According to American authorities, British and American intelligence services possessed intercepts that Ukrainian intelligence services were not privy to. The names of Ukrainian officials the Russians intended to assassinate or arrest, as well as the Ukrainians the Kremlin wished to place in positions of authority, were included in the new intelligence.

Even although C.I.A. director Mr. Burns hurried to Kyiv in January 2022 to brief President Zelensky and a few of his top advisors, they didn’t seem to be persuaded.

C.I.A. and MI6 officers paid their counterparts in Ukraine their farewell visits in Kyiv as the Russian invasion drew closer. Fearing they would be killed by the Russians, one of the MI6 officers broke down in tears in front of the Ukrainians.

A small group of C.I.A. officers were moved to a hotel complex in western Ukraine and were spared from the larger U.S. evacuation at Mr. Burns’s request. They were unwilling to leave their lovers behind.

No Endgame

The only American government personnel on the ground following Mr. Putin’s invasion on February 24, 2022, were the C.I.A. agents stationed in the hotel. They met with their Ukrainian connections every day at the hotel to exchange information. The previous handcuffs were removed, and the Biden White House gave intelligence agencies permission to support deadly actions against Russian soldiers within the borders of Ukraine.

The C.I.A. briefings were often surprisingly detailed.

Eighth day of the conflict, March 3, 2022, saw the C.I.A. squad provide an accurate two-week preview of Russian preparations. That same day, the Russians would open a humanitarian corridor out of the besieged city of Mariupol, and as the Ukrainians used it, they would commence fire on them.

According to the C.I.A., the Russians intended to encircle the important port city of Odesa; however, a storm postponed the attack, and the Russians were never able to capture the city. The Russians then planned to attack six Ukrainian cities on March 10 and had already programmed cruise missile coordinates for those attacks.

Moreover, Mr. Zelensky and other senior Ukrainian leaders were targets of assassination attempts by the Russians. According to a senior Ukrainian official, in at least one instance the C.I.A. supplied intelligence with the domestic agency in Ukraine, helping to thwart a plan against the president.

As Republicans in the House consider whether to stop providing billions of dollars in help, some Ukrainian intelligence personnel are already questioning their American counterparts about whether the C.I.A. will desert them. A senior Ukrainian military stated, “It happened in Afghanistan before and it will happen in Ukraine now.”

“We have demonstrated a clear commitment to Ukraine over many years, and this visit was another strong signal that the U.S. commitment will continue,” a C.I.A. official said in reference to Mr. Burns’s visit to Kyiv last week.

In addition to the 12 forward operating bases, which General Kondratiuk claims are still in use, the C.I.A. and the HUR have constructed two more secret bases to intercept Russian communications. As a result, the HUR is currently gathering and producing more intelligence than it has at any other point during the war, much of which it shares with the C.I.A.

General Dvoretskiy declared, “You can’t get information like this anywhere—except here, and now.”