of Soviet hostilities with Poland; that clause would lead to questions regarding the issue of Lithuanian neutrality in the ongoing Polish-Soviet War. Lithuania was to stop the activities of the "anti-Soviet organisations and groups" on its territory, including the activities of the exiled bodies of the Belarusian People's Republic. Aftermath Polish–Lithuanian conflict While the treaty was being negotiated and signed, most of the territory granted by the treaty to Lithuania was already controlled by Bolshevik forces. As the Poles were retreating from western Russia, Lithuania attempted to secure the borders outlined in the treaty. Lithuanian forces crossed the Foch line on July 19, seeking to take control of the territories granted to Lithuania by the Soviet Union, advancing rapidly despite Polish protests and, in several cases, fighting skirmishes with the retreating Polish forces. That led to clashes in southern Lithuania over the towns of Sejny, Augustów and Suwałki. According to historian Piotr Lossowski, the Lithuanians also provided the Soviets with logistical support. The Bolshevik forces were the first to enter Vilnius on July 14, 1920, although the treaty did not transfer it to the Lithuanians. The Soviets installed a puppet government, the former Litbel, with the intent of fomenting a socialist revolution. Leon Trotsky and Mikhail Tukhachevsky were preparing the overthrow of the Lithuanian government. The plans never came to pass since Poland defeated Soviet forces in the Battle of Warsaw between August 13 and August 25. On August 26, as the Polish Army was approaching the southern borders of Lithuania, the Soviets finally transferred Vilnius to Lithuanian control and the Red Army retreated. In September, when the Poles had gained an upper hand and were pursuing the Soviets back to the east, Soviet forces moved at will through Lithuanian-controlled territory, but Polish forces that tried to pursue them were arrested and interned. Lithuania's declared neutrality was challenged by Poland, which accused Lithuania of allowing free Soviet passage through its territory, which Lithuania could not deny. The treaty did not create a formal military alliance between the Soviets and the Lithuanians but it diminished Lithuania's standing as a neutral state. Łossowski wrote that Lithuania's lack of neutrality towards Poland was such that "the Polish government could have with full justification treated Lithuania as a country participating in the war on the other side, with all of its political and legal implications". Historian Alfred E. Senn wrote that "the Lithuanians cannot