But a New York Times investigation reveals that America was woven into the war far more intimately and broadly than previously understood. At critical moments, the partnership was the backbone of Ukrainian military operations that, by U.S. counts, have killed or wounded more than 700,000 Russian soldiers. (Ukraine has put its casualty toll at 435,000.) Side by side in Wiesbaden’s mission command center, American and Ukrainian officers planned Kyiv’s counteroffensives. A vast American intelligence-collection effort both guided big-picture battle strategy and funneled precise targeting information down to Ukrainian soldiers in the field.
An early proof of concept was a campaign against one of Russia’s most-feared battle groups, the 58th Combined Arms Army. In mid-2022, using American intelligence and targeting information, the Ukrainians unleashed a rocket barrage at the headquarters of the 58th in the Kherson region, killing generals and staff officers inside. Again and again, the group set up at another location; each time, the Americans found it and the Ukrainians destroyed it.
Farther south, the partners set their sights on the Crimean port of Sevastopol, where the Russian Black Sea Fleet loaded missiles destined for Ukrainian targets onto warships and submarines. At the height of Ukraine’s 2022 counteroffensive, a predawn swarm of maritime drones, with support from the Central Intelligence Agency, attacked the port, damaging several warships and prompting the Russians to begin pulling them back.
But ultimately the partnership strained — and the arc of the war shifted — amid rivalries, resentments and diverging imperatives and agendas.
The Ukrainians sometimes saw the Americans as overbearing and controlling — the prototypical patronizing Americans. The Americans sometimes couldn’t understand why the Ukrainians didn’t simply accept good advice.
On a tactical level, the partnership yielded triumph upon triumph. Yet at arguably the pivotal moment of the war — in mid-2023, as the Ukrainians mounted a counteroffensive to build victorious momentum after the first year’s successes — the strategy devised in Wiesbaden fell victim to the fractious internal politics of Ukraine: The president, Volodymyr Zelensky, versus his military chief (and potential electoral rival), and the military chief versus his headstrong subordinate commander. When Mr. Zelensky sided with the subordinate, the Ukrainians poured vast complements of men and resources into a finally futile campaign to recapture the devastated city of Bakhmut. Within months, the entire counteroffensive ended in stillborn failure.
The partnership operated in the shadow of deepest geopolitical fear — that Mr. Putin might see it as breaching a red line of military engagement and make good on his often-brandished nuclear threats. The story of the partnership shows how close the Americans and their allies sometimes came to that red line, how increasingly dire events forced them — some said too slowly — to advance it to more perilous ground and how they carefully devised protocols to remain on the safe side of it.
Time and again, the Biden administration authorized clandestine operations it had previously prohibited. American military advisers were dispatched to Kyiv and later allowed to travel closer to the fighting. Military and C.I.A. officers in Wiesbaden helped plan and support a campaign of Ukrainian strikes in Russian-annexed Crimea. Finally, the military and then the C.I.A. received the green light to enable pinpoint strikes deep inside Russia itself.
In some ways, Ukraine was, on a wider canvas, a rematch in a long history of U.S.-Russia proxy wars — Vietnam in the 1960s, Afghanistan in the 1980s, Syria three decades later.
It was also a grand experiment in war fighting, one that would not only help the Ukrainians but reward the Americans with lessons for any future war.
Inside the U.S. European Command, this process gave rise to a fine but fraught linguistic debate: Given the delicacy of the mission, was it unduly provocative to call targets “targets”?
Some officers thought “targets” was appropriate. Others called them “intel tippers,” because the Russians were often moving and the information would need verification on the ground.
The debate was settled by Maj. Gen. Timothy D. Brown, European Command’s intelligence chief: The locations of Russian forces would be “points of interest.” Intelligence on airborne threats would be “tracks of interest.”
“If you ever get asked the question, ‘Did you pass a target to the Ukrainians?’ you can legitimately not be lying when you say, ‘No, I did not,’” one U.S. official explained.
The way the system worked, Task Force Dragon would tell the Ukrainians where Russians were positioned. But to protect intelligence sources and methods from Russian spies, it would not say how it knew what it knew. All the Ukrainians would see on a secure cloud were chains of coordinates, divided into baskets — Priority 1, Priority 2 and so on. As General Zabrodskyi remembers it, when the Ukrainians asked why they should trust the intelligence, General Donahue would say: “Don’t worry about how we found out. Just trust that when you shoot, it will hit it, and you’ll like the results, and if you don’t like the results, tell us, we’ll make it better.”
At the White House, Mr. Biden and his advisers weighed that argument against fears that pushing the Russians would only lead Mr. Putin to panic and widen the war. When the generals requested HIMARS, one official recalled, the moment felt like “standing on that line, wondering, if you take a step forward, is World War III going to break out?” And when the White House took that step forward, the official said, Task Force Dragon was becoming “the entire back office of the war.”
Mr. Zelensky was hoping to attend the mid-September meeting of the United Nations General Assembly. A showing of progress on the battlefield, he and his advisers believed, would bolster his case for additional military support. So they upended the plan at the last minute — a preview of a fundamental disconnect that would increasingly shape the arc of the war.
The Ukrainians were already exerting pressure on the ground. And the Biden administration had authorized helping the Ukrainians develop, manufacture and deploy a nascent fleet of maritime drones to attack Russia’s Black Sea Fleet. (The Americans gave the Ukrainians an early prototype meant to counter a Chinese naval assault on Taiwan.) First, the Navy was allowed to share points of interest for Russian warships just beyond Crimea’s territorial waters. In October, with leeway to act within Crimea itself, the C.I.A. covertly started supporting drone strikes on the port of Sevastopol.
That same month, U.S. intelligence overheard Russia’s Ukraine commander, Gen. Sergei Surovikin, talking about indeed doing something desperate: using tactical nuclear weapons to prevent the Ukrainians from crossing the Dnipro and making a beeline to Crimea.
Until that moment, U.S. intelligence agencies had estimated the chance of Russia’s using nuclear weapons in Ukraine at 5 to 10 percent. Now, they said, if the Russian lines in the south collapsed, the probability was 50 percent.
The planning for 2023 began straightaway, at what in hindsight was a moment of irrational exuberance.
Ukraine controlled the west banks of the Oskil and Dnipro rivers. Within the coalition, the prevailing wisdom was that the 2023 counteroffensive would be the war’s last: The Ukrainians would claim outright triumph, or Mr. Putin would be forced to sue for peace.
“We’re going to win this whole thing,” Mr. Zelensky told the coalition, a senior American official recalled.
To accomplish this, General Zabrodskyi explained as the partners gathered in Wiesbaden in late autumn, General Zaluzhny was once again insisting that the primary effort be an offensive toward Melitopol, to strangle Russian forces in Crimea — what he believed had been the great, denied opportunity to deal the reeling enemy a knockout blow in 2022.
And once again, some American generals were preaching caution.
At the Pentagon, officials worried about their ability to supply enough weapons for the counteroffensive; perhaps the Ukrainians, in their strongest possible position, should consider cutting a deal. When the Joint Chiefs chairman, General Milley, floated that idea in a speech, many of Ukraine’s supporters (including congressional Republicans, then overwhelmingly supportive of the war) cried appeasement.
Several weeks later, at a meeting in Kyiv, the Ukrainian commander had locked General Cavoli in a Defense Ministry kitchen and, vaping furiously, made one final, futile plea. “He was caught between two fires, the first being the president and the second being the partners,” said one of his aides.
The red lines kept moving.
There were the ATACMS, which arrived secretly in early spring, so the Russians wouldn’t realize Ukraine could now strike across Crimea.
And there were the SMEs. Some months earlier, General Aguto had been allowed to send a small team, about a dozen officers, to Kyiv, easing the prohibition on American boots on Ukrainian ground. So as not to evoke memories of the American military advisers sent to South Vietnam in the slide to full-scale war, they would be known as “subject matter experts.” Then, after the Ukrainian leadership shake-up, to build confidence and coordination, the administration more than tripled the number of officers in Kyiv, to about three dozen; they could now plainly be called advisers, though they would still be confined to the Kyiv area.
The Russian offensive exposed a fundamental asymmetry: The Russians could support their troops with artillery from just across the border; the Ukrainians couldn’t shoot back using American equipment or intelligence.
Yet with peril came opportunity. The Russians were complacent about security, believing the Americans would never let the Ukrainians fire into Russia. Entire units and their equipment were sitting unsheltered, largely undefended, in open fields.
The Ukrainians asked for permission to use U.S.-supplied weapons across the border. What’s more, Generals Cavoli and Aguto proposed that Wiesbaden help guide those strikes, as it did across Ukraine and in Crimea — providing points of interest and precision coordinates.
The White House was still debating these questions when, on May 10, the Russians attacked.
This became the moment the Biden administration changed the rules of the game. Generals Cavoli and Aguto were tasked with creating an “ops box” — a zone on Russian soil in which the Ukrainians could fire U.S.-supplied weapons and Wiesbaden could support their strikes.
At first they advocated an expansive box, to encompass a concomitant threat: the glide bombs — crude Soviet-era bombs transformed into precision weapons with wings and fins — that were raining terror on Kharkiv. A box extending about 190 miles would let the Ukrainians use their new ATACMS to hit glide-bomb fields and other targets deep inside Russia. But Mr. Austin saw this as mission creep: He did not want to divert ATACMS from Lunar Hail.
Instead, the generals were instructed to draw up two options — one extending about 50 miles into Russia, standard HIMARS range, and one nearly twice as deep. Ultimately, against the generals’ recommendation, Mr. Biden and his advisers chose the most limited option — but to protect the city of Sumy as well as Kharkiv, it followed most of the country’s northern border, encompassing an area almost as large as New Jersey. The C.I.A. was also authorized to send officers to the Kharkiv region to assist their Ukrainian counterparts with operations inside the box.
The unthinkable had become real. The United States was now woven into the killing of Russian soldiers on sovereign Russian soil.
Longstanding policy barred the C.I.A. from providing intelligence on targets on Russian soil. So the administration would let the C.I.A. request “variances,” carve-outs authorizing the spy agency to support strikes inside Russia to achieve specific objectives.
Mr. Austin would later recount how he contemplated this manpower mismatch as he looked out the window of his armored S.U.V. snaking through the Kyiv streets. He was struck, he told aides, by the sight of so many men in their 20s, almost none of them in uniform. In a nation at war, he explained, men this age are usually away, in the fight.
Mr. Zelensky had already taken a small step, lowering the draft age to 25. Still, the Ukrainians hadn’t been able to fill existing brigades, let alone build new ones.
Mr. Austin pressed Mr. Zelensky to take the bigger, bolder step and begin drafting 18-year-olds. To which Mr. Zelensky shot back, according to an official who was present, “Why would I draft more people? We don’t have any equipment to give them.”
To one American official, though, it’s “not an existential war if they won’t make their people fight.”
General Baldwin, who early on had crucially helped connect the partners’ commanders, had visited Kyiv in September 2023. The counteroffensive was stalling, the U.S. elections were on the horizon and the Ukrainians kept asking about Afghanistan.
The Ukrainians, he recalled, were terrified that they, too, would be abandoned. They kept calling, wanting to know if America would stay the course, asking: “What will happen if the Republicans win the Congress? What is going to happen if President Trump wins?’”
In his last, lame-duck weeks, Mr. Biden made a flurry of moves to stay the course, at least for the moment, and shore up his Ukraine project.
He crossed his final red line — expanding the ops box to allow ATACMS and British Storm Shadow strikes into Russia — after North Korea sent thousands of troops to help the Russians dislodge the Ukrainians from Kursk. One of the first U.S.-supported strikes targeted and wounded the North Korean commander, Col. Gen. Kim Yong Bok, as he met with his Russian counterparts in a command bunker.
The administration also authorized Wiesbaden and the C.I.A. to support long-range missile and drone strikes into a section of southern Russia used as a staging area for the assault on Pokrovsk, and allowed the military advisers to leave Kyiv for command posts closer to the fighting.
In December, General Donahue got his fourth star and returned to Wiesbaden as commander of U.S. Army Europe and Africa. He had been the last American soldier to leave in the chaotic fall of Kabul. Now he would have to navigate the new, unsure future of Ukraine.