Ukraine is marking Saturday two years since Russia’s full-scale invasion, with a string of foreign dignitaries and officials expected to visit the capital, Kyiv, in solidarity as Ukrainian forces run low on ammunition and weaponry and Western aid hangs in the balance.

A somber mood hangs over the country as the war against Russia enters its third year, and Kyiv's troops face mounting challenges on the front line amid dwindling ammunition supplies and personnel challenges, and having withdrawn from a strategic eastern city that handed Moscow one of its biggest victories.

The anniversary comes after President Volodymyr Zelenskyy sacked top military commander Valerii Zaluzhnyi, replacing him with Col. Gen. Oleksandr Syrskyi, marking the most significant shakeup of top brass since the full-scale invasion.

Russia still controls roughly a quarter of the country after Ukraine failed to meet expectations with its summer-time counteroffensive not producing major breakthroughs. Meanwhile, millions of Ukrainians continue to live under precarious circumstances in the crossfire of battles, and many others face constant struggles under Russian occupation. Most are still waiting for a Ukrainian liberation that hasn't come.

Foreign officials are expected to descend on the capital to meet with Zelenskyy and other Ukrainian officials and express their continued support for the country as it fights Moscow's troops and prepares for European Union membership.

In the U.S. Congress, Republicans have stalled $60 billion in military aid for Kyiv, desperately needed in the short term. The EU recently approved a 50 billion euro (about $54 billion) aid package for Ukraine, despite resistance from Hungary, meant to support Ukraine's economy.

U.S. President Joe Biden tied the loss of the defensive stronghold of Avdiivka in the Donetsk region after months of grueling battles to the stalled U.S. aid. Fears have since spiked that Ukrainian forces would face similar difficulties across other parts of the 1000-kilometer (620-mile) front line as they come under mounting pressure from Russian assaults.