Complex sentence: However, the dogs were trained with stationary Russian tanks and very seldom ran under moving tanks, instead being shot as they ran beside moving tanks, and when both Russian and German tanks were present the dogs would preferentially run towards the familiar Russian tanks.
Split into simpler sentences: However, the dogs were trained with stationary Russian tanks and very seldom ran under moving tanks, instead being shot as they ran beside moving tanks. When both Russian and German tanks were present, the dogs would preferentially run towards the familiar Russian tanks.