Tense Ukrainian soldiers with assault rifles creep stealthily around mock houses before bursting in to clear out gunmen, while others practice setting ambushes or infantry assaults — all under the watchful eyes of U.S. Army trainers.

Dotted around the vast, wooded Yavoriv military training area in western Ukraine, soldiers of the U.S. 173rd Airborne Brigade are instructing Ukrainian national guardsmen in techniques designed to help them in the simmering war against pro-Russian separatists hundreds of kilometers to the east.

Although Western countries have held back from military involvement in the conflict, the small-scale U.S. training effort — together with similar programs set up by Britain, Canada and Poland — sends a signal to Russia that the West stands behind the Ukrainian government.