The conflict in Ukraine has reached a crucial point, with President Trump pursuing a reconciliation with Russia’s leader, Vladimir V. Putin, and advocating for an end to the hostilities.

However, for almost three years before Mr. Trump’s potential return to power, there was a unique collaboration between the United States and Ukraine involving intelligence, strategy, military planning, and technology. The nature and specifics of this alliance were understood by only a select group of American and allied officials.

Remarkably, the Pentagon has disclosed publicly the $66.5 billion worth of weaponry provided to Ukraine. Yet, a New York Times investigation reveals that the United States’ involvement in the conflict went far beyond what was previously known. The covert partnership impacted not only the overall strategy of the conflict but also provided precise targeting data to Ukrainian soldiers on the ground.

The following are five key findings from the investigation.

A U.S. base in Wiesbaden, Germany, supplied the Ukrainians with the coordinates of Russian forces on their soil.

The rationale behind the collaboration was that America’s close partnership with Ukraine would counterbalance Russia’s significant advantages in both manpower and armaments. To assist the Ukrainians in deploying their increasingly sophisticated weaponry, the Americans established an operation known as Task Force Dragon.

At the core of the alliance was the U.S. Army garrison in Wiesbaden, Germany. Daily, U.S. and Ukrainian military officers set priorities for targeting — Russian units, equipment, or infrastructure. American and coalition intelligence officials analyzed satellite imagery, radio signals, and intercepted communications to locate Russian positions. Task Force Dragon then provided the coordinates to the Ukrainians so they could engage these targets.

There was concern that identifying the targets as such could be too provocative. As a result, they were referred to as “points of interest.”

U.S. intelligence and artillery helped Ukraine quickly turn the tide against the Russian invasion.

In the spring of 2022, the Biden administration agreed to supply High Mobility Artillery Rocket Systems (HIMARS), which utilized satellite-guided munitions for strikes up to 50 miles away.

In the conflict’s first year, the Ukrainians were heavily reliant on American intelligence, and Task Force Dragon was responsible for verifying and overseeing nearly every HIMARS strike.

The strikes led to a significant rise in Russian casualties, and Ukraine’s 2022 counteroffensive was largely successful: by December, the Ukrainians maintained an unlikely advantage against the Russian forces.

The Biden administration kept moving its red lines.

From the start, administration officials aimed to establish clear boundaries: America was not at war with Russia; it was aiding Ukraine. However, they also feared that actions taken to achieve this support could provoke Putin to strike at NATO targets or follow through on his nuclear threats. Despite growing comfortable with the risks to assist Ukraine in confronting the evolving threats, many of the most provocative steps were taken in secret.

• There was a relaxation on the ban against U.S. military personnel being on Ukrainian soil; as a result, about a dozen military advisers were placed in Kyiv. Initially, the Pentagon referred to them as “subject matter experts” to avoid attention, but the team later expanded to around three dozen and was allowed to visit Ukrainian command posts nearing the conflict zones.

• In 2022, the U.S. Navy received authorization to share targeting data for Ukrainian drone strikes on warships just beyond the territorial waters of Russian-annexed Crimea. The CIA was also permitted to support Ukrainian operations within the Crimean waters, and in the fall of that year, covertly aided in Ukrainian drone strikes on Russian warships at the port of Sevastopol.

• In January 2024, U.S. and Ukrainian military officers in Wiesbaden collaborated on a campaign — utilizing coalition-supplied long-range missiles and Ukrainian drones — to target approximately 100 Russian military objectives across Crimea. The campaign, named Operation Lunar Hail, largely succeeded in compelling the Russians to withdraw equipment, infrastructure, and forces from Crimea to the Russian mainland.

Ultimately, the U.S. military and C.I.A. were allowed to help with strikes into Russia.

The firmest redline was Russia’s border. But in the spring of 2024, in order to protect the northern city of Kharkiv against a Russian onslaught, the administration permitted the creation of an “ops box” — a zone within Russian territory where U.S. officers in Wiesbaden could provide the Ukrainians with precise coordinates. The initial zone covered a wide area of Ukraine’s northern border. Following North Korea’s deployment of troops to aid in Ukraine’s incursion into Russia’s Kursk region, the zone was enlarged. The U.S. military was subsequently authorized to enable missile strikes in southern Russia where the Russians were preparing their forces and equipment for their eastern Ukraine offense.

Traditionally, the CIA was barred from providing intelligence on targets within Russian territory. But the CIA could apply for “variances,” allowing for exceptions to support specific strikes. Intelligence had located a massive munitions depot in Toropets, 290 miles north of the Ukrainian border. On September 18, 2024, a swarm of drones struck the depot. The explosion, equivalent in power to a minor earthquake, created a crater the length of a football field. Later, the CIA obtained permission to facilitate Ukrainian drone strikes in southern Russia in an effort to slow the Russian advances in eastern Ukraine.

Political disagreements in Ukraine contributed to the 2023 counteroffensive’s collapse.

The 2023 counteroffensive intended to build on the successes of the first year. Nonetheless, despite strategic war games in Wiesbaden and the agreement on tactics, the plan was at odds with Ukrainian politics.

Ukraine’s armed forces chief, Gen. Valery Zaluzhny, backed the strategy, which aimed at an assault toward the southern city of Melitopol that would sever Russian supply lines. However, his rival and junior, Col. Gen. Oleksandr Syrsky, proposed a different plan — to pin down Russian forces in the occupied eastern city of Bakhmut. Ukrainian President Volodymyr Zelensky sided with Syrsky, dividing the ammunition and forces between two primary fronts instead of concentrating them in one. The Ukrainians failed to retake Bakhmut, and within months, the counteroffensive ended in failure. Russia then gained the upper hand.