The Poles and the Soviets re-established diplomatic relations in 1941 , following the Sikorski – Mayski Agreement ; but the Soviets broke them off again in 1943 after the Polish government demanded an independent examination of the recently discovered Katyn burial pits ( Katyn massacre ) . The Soviets then lobbied the Western Allies to recognise the pro-Soviet Polish government of Wanda Wasilewska in Moscow
Katyn massacre
Katyn massacre
Soviet invasion of Poland