KUPIANSK, Ukraine — The Ukrainian soldiers rose in the predawn, stretching, rubbing their eyes and rolling up sleeping bags in a basement hideout near the front line in the country’s east. Their day would not take them far afield. Most stayed in the basement, working with keyboards and joysticks controlling drones.

At a precarious moment for Ukraine, as the country wobbles between hopes that President Donald Trump’s ceasefire talks will end the war and fears that the United States will withdraw military support, the soldiers were taking part in a Ukrainian army initiative that Ukraine hopes will allow it to stay in the fight absent American weapons.

Should the peace talks fail, or the United States discontinue arms shipments, the Ukrainian drone initiative is likely to take on more importance. The program doubles down on unmanned systems that are assembled in Ukraine, mostly small exploding drones flown from basement shelters.

On Monday, Russian President Vladimir Putin added to the many uncertainties in the war by ordering a three-day ceasefire in Ukraine this month, though it is unclear if such a pause would hold, or even start. That announcement followed a week of unabated warfare in Ukraine, including the deadliest attack on Kyiv, the capital, in nearly a year, and of conflicting signals about what would come next from the Trump administration.

Trump has been less critical of Ukraine’s leadership in recent days, instead rebuking Putin for his continuing bombardment of Ukraine. But Trump has still not promised more weapons, which remain crucial.

A U.S. decision to discontinue military aid would leave Ukraine vulnerable along the front and far beyond. Its army relies on Patriot interceptors as its only defense against Russian ballistic missile attacks on Kyiv. Ukraine’s military also lacks its own medium-range missiles, such as those fired by the American-made HIMARS system, which are key to striking Russian troops and gear before they reach the front line.

And earlier, Ukrainian innovations in the war, like Ukraine’s fleet of remote-controlled, exploding speedboats that sank much of Russia’s Black Sea Fleet, were introduced to great effect only for Russia to devise countermeasures.

Still, the Ukrainians have beaten the odds before in their battle against a much larger enemy, in part because they changed battlefield strategy and rejiggered weapons on the fly. At least for now, soldiers are hopeful that the latest innovative program, called the Line of Drones, will help them keep the Russians mainly stalled on the front line.

“It’s not man against man anymore,” said the commander of the squad operating from the basement in eastern Ukraine.

The group flies first-person-view drones, which give the pilot the video equivalent of a front-row seat as bombs hurtle into Russian soldiers, cars, tanks or bunkers. In keeping with military protocol, the commander asked to be identified only by his first name and rank, Pvt. Artem.

Even before the Line of Drones, Ukraine was relying heavily on unmanned weapons, which now inflict about 70% of all casualties in the war on both sides, the Ukrainian military says — more than all other weapons combined, including tanks, howitzers, mortars and land mines. While those other weapons are partly provided by the United States, the Ukrainians assemble the drones domestically from components mostly made in China.

The expanded drone program, in the works since last fall but formally announced in February, is Ukraine’s Plan B if talks to end the war, which began with Russia’s full-scale invasion in 2022, fail.

Drones from both sides already hum near continuously over the battlefield. In the drone war, Russia has an advantage in quantity, while Ukraine has an advantage in quality, often becoming a first adopter of new technological approaches. Those include flying retransmitter drones to extend the explosive drones’ range and guiding drones with hair-thin fiber-optic threads that are impervious to Russian forces’ own innovations in jamming.

The Line of Drones strategy has been overshadowed by the ceasefire talks and by Trump’s earlier dismissive assessment of Ukraine’s chances without U.S. aid. (“You don’t have the cards,” he told Ukrainian President Volodymyr Zelenskyy at a contentious Oval Office meeting.) But the drone deployment has already yielded results, according to military analysts.

It has been partly credited for a three-month slowdown of the Russian offensive in Ukraine. Russian forces that surged forward last fall have been in a virtual stall since January, despite the Russian military’s staging costly assaults.

All wars spur innovation, such as the invention of radar during World War II and night-vision goggles in Vietnam. But Ukraine’s drone strategy was also born of a major weakness of its military after more than three years of war: the waning motivation of Ukrainians to join the army.

Drones don’t replace troops; in fact, each flight of a first-person-view drone can require up to four soldiers. For flights last week, a drone squad consisted of a pilot, a navigator, an armorer and a pilot of a retransmitting drone.

With fewer soldiers to lose than Russia, Ukraine wants to limit direct engagements. That’s where the drones come in.