Nearly 300 U.S. troops arrived in Ukraine on Friday as a part of a long-planned U.S. mission to provide training for Ukrainian National Guard forces. But with the country’s year-old war seemingly still far from a lasting diplomatic resolution, it is not at all clear whether the U.S. mission can discernably change the equation on the ground — nor whether it would respond in kind should Russia decided to further ratchet up its support for pro-Russian rebels as a result.

The U.S. training mission was announced last summer, and its implementation — originally expected in March — was delayed after negotiations in Minsk, Belarus in February led to a cease-fire deal that still officially holds between Ukrainian forces and Russian-backed separatists.

Despite that cease-fire, violence has continued from each side, albeit at a slightly diminished rate. The U.N. Human Rights Commissioner said Friday that 6,116 people have been killed in Ukraine’s year of fighting.

The Ukrainian National Guard has taken on an increasingly important role in the war over the course of the past year. The Ukrainian government, facing major economic woes and aware of the outdated and under-funded status of its regular forces, has relied on the guardsmen, many of whom were previously serving in all-volunteer units.

Some the guardsmen are currently playing a major role in holding the town of Shyrokyne, which lies on the eastern front of Ukrainian-controlled territory, just east of the strategically important port city of Mariupol.

Writing in the New York Review of Books, noted Eastern Europe analyst Tim Judah said, “The test of whether the conflict has reached a stalemate will come at Mariupol.”

If pro-Russian rebels were to capture Mauripol, as many Ukrainians fear they may try, the separatists would gain a land corridor between Russia and Crimea, which Russia annexed last year.

But the role of Ukrainian militia groups, which together form part of the National Guard, has been the source of some controversy. One of the most battle-hardened groups fighting to defend Ukraine’s east is called the Azov Battalion, a faction which displays Nazi insignia on its banners and whose members include neo-Nazis.

During the course of the conflict, Russia has continually used the specter of groups like these as a pretext for its defense of ethnic Russians it says are under attack in Ukraine.

The Russian foreign ministry referred to the 900 guardsmen the U.S. would be training as "ultranationalists ... who stained themselves with the blood of women, children and the elderly during their punitive operations."

In an email to Al Jazeera, U.S Embassy spokesperson James Hallock said the U.S. training would not include members of the Azov Battalion, and the State Department said Friday that the mission would have a vetting process for any forces it trains.

Moscow, which accuses the United States of meddling in Ukraine — a place many Russians are seen as considering their country’s back yard — reacted bitterly to the arrival of U.S. troops.

Dmitry Peskov, spokesman for Russian President Vladimir Putin, said, "The participation of instructors and specialists from a third country on the territory of Ukraine, where an unresolved intra-Ukrainian conflict remains, where problems persist in carrying out the Minsk agreement, is far from helping resolve the conflict.”

“To the contrary, it enables destabilizing the situation,” Peskov said.

For now, part of the Obama administration’s calculus may be to try and drive up the costs of Moscow’s support of pro-Russian separatists in the conflict, while still claiming that U.S. actions do not represent a drastic policy shift.

This seemed to be implied in State Department spokeswoman Marie Harf’s answer to a question on Friday about the U.S. training mission, which is being jointly conducted with the Department of Defense.

“We’ve been doing this with Ukraine, I think, for about the last 20 years in some form or fashion, so this isn’t new,” Harf said. But when pressed about whether the training was different this time around, she added, “Obviously, there’s the reality of the situation in eastern Ukraine. So this is part of our ongoing effort, but of course, we’re all aware of the situation there.”

The Obama administration has thus far rebuffed calls to directly provide arms to Ukraine — something many in Congress have urged, as have many former Obama administration officials. The president and some of his advisers fear a military escalation in the conflict could provoke an aggressive response from Russia, which has shown its willingness to pursue military actions in Ukraine despite a very weak economy at home.

In the meantime, forces on the ground in Ukraine remain far apart in their demands and what they might be able to achieve.

“On the Ukrainian side the maximum and, for now, unattainable objective is to re-conquer the lost eastern territories,” Judah wrote. “What is far more realistic, though, is for Ukraine to hold the line to prevent further losses, while over the next few years its armed forces are transformed into a far more formidable fighting force.”

That is likely a scenario that the Obama administration is trying to support.

But from the pro-Russian rebel perspective, even as their military campaign has stalled of late, there are no signs of their leaders dampening their maximalist, separatist aims.

On Saturday, a separatist leader with the self-proclaimed Donetsk People’s Republic in the heart of rebel-held eastern Ukraine told the BBC that the Minsk cease-fire risked falling apart should Ukraine not accept independence for separatist territory in the country's east — something that Kiev considers a non-starter.

“The Minsk truce will not end confrontation, but rather recognize it,” Dmitri Trenin, director of the Carnegie Moscow Center, wrote in the The National Interest, an international affairs periodical, at the time of February’s cease-fire.

Two months on, that situation remains largely the same — a fact that some 300 U.S. troops are unlikely to change in the near term.

With the Associated Press