A deafening explosion shakes the ground, sending lumps of dirt and smoke into the air, breaking the seeming tranquility of a cold January morning in the frozen fields of war-torn Ukraine's eastern Donbas region.
After almost two years of grinding trench warfare against invading Russian troops, some 30% of Ukrainian territory is thought to be littered with unexploded mines.
"The Russians connect the mines," said Sergeant Boller, a Ukrainian sapper teaching recruits.