Complex sentence: During World War II, and following the Soviet invasion of eastern Poland, a wave of anti-Polish repression by the Soviet Secret Police was conducted between 1939 and 1941, coupled with a successful Soviet attack against a Polish partisan unit stationed in the Kobielne Wilderness.
Split into simpler sentences: During World War II, and following the Soviet invasion of eastern Poland, a wave of anti-Polish repression by the Soviet Secret Police was conducted between 1939 and 1941. It was coupled with a successful Soviet attack against a Polish partisan unit stationed in the Kobielne Wilderness.