Frowning, Sergeant Andriy stands on a mound of earth, arranged in a straight line. Birds sing around him, even as the sound of explosions comes from the horizon. At his feet, a man armed with a small shovel and a blue bucket pokes his head out of a hole. He is carving steps into the ground, digging trenches and shelters in case the Ukrainian army is forced to fall back. "This is considered the second line of defence" explains Andriy, "there is the first line of defence, and a second line of defence in case the enemy proceeds with a heavy assault". This close to enemy positions, Ukraine's military engineers -- or sappers -- can't work with excavation machinery as it can be easily spotted. Everything must be done by hand, by the soldiers. "They are trained on training grounds. Engineers and sappers show them how to do it... That's why everyone knows what a trench or a shelter should look like" says Yevgen, the youngest soldier in the battalion. IMAGES AND SOUNDBITES