sentences:  Due to British mediation and pressure, the Soviet Union and the Polish government-in-exile (then based in London) re-established Polish-Soviet diplomatic relations in July 1941 after the German invasion of the Soviet Union started on 22 June 1941.The Sikorski–Mayski agreement of 30 July 1941 resulted in the Soviet Union agreeing to invalidate the territorial aspects of the pacts it had had with Nazi Germany and to release tens of thousands of Polish prisoners-of-war held in Soviet camps.Pursuant to the agreement between the Polish government-in-exile and the Soviet Union, the Soviets granted "amnesty" to many Polish citizens, from whom a military force was formed.