After the Soviet invasion of September 1939, in October the USSR handed Wilno and part of the Wilno region to Lithuania, while the rest of the region, including Lida, Oszmiana and Mołodeczno, remained in the Belorussian SSR. In June 1941 the NKVD deported Polish officials, officers, policemen and landowners from here, together with their families; for the Poles of the Wilno region this was the first mass deportation. In July 1944 the Home Army launched Operation Tempest here, including its attack on Wilno.
1939
- 1 September – 6 October 1939BattleInvasion of PolandFrom 1 September to 6 October 1939 Poland fought Nazi Germany, Slovakia and, from 17 September, the Soviet Union. The campaign ended in partition.
- 17 September – 6 October 1939BattleSoviet invasion of PolandFrom 17 September 1939 the Red Army occupied eastern Poland, resisted by the KOP, Grodno, Lwów and Orlik-Rückemann's group. Fighting went on into October.
- 10 October 1939EventThe Soviet–Lithuanian Mutual Assistance TreatyOn 10 October 1939 Lithuania signed a mutual assistance pact in Moscow. It received Wilno, seized from Poland, but had to accept 20,000 Soviet troops.