Poland gained nominal status as a puppet state of Germany through the Treaty of Brest-Litovsk. But the renunciation of that Treaty in the Armistice of November 1918 threatened its existence. Soviet Russia invaded, looking to recoup the territories it had conceded at Brest-Litovsk, but the Poles crushed the invaders at the Battle of Warsaw, forcing Russia to sue for peace. The resultant Treaty of Riga in March 1921 awarded Poland an additional 52,000 square miles (135,000 square km) of territory to the east of the Curzon line, a demarcation suggested by the then British Foreign Secretary in 1919. Czechoslovakia declared its independence on 28 October 1918 during the disintegration of the Austro-Hungarian Empire and went on to seize some territory from southern Poland the following year. The new state harboured substantial German and Hungarian minorities around its western and eastern borders respectively, which would later be a cause of contention.
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