What do you think were stalin's major goals during world war 2? how did he work with roosevelt and churchill to achieve these goals?

Our idea of the wartime 'Big Three' may be derived from their photographs together at Teheran in 1943 and at Yalta in 1945; it is well to be reminded that these were the only occasions at which they met as a group. On the other hand, Churchill and Roosevelt met together on eleven occasions (including the Atlantic Conference before the US entered the war) and Churchill and Stalin on three occasions. Roosevelt and Stalin never met except on the margins of the two trilateral meetings. In so far as a triumvirate existed, it was a matter of communications through messages or intermediaries. Room for misunderstanding was always present. How could this not be the case since their countries, their personal philosophies and national objectives were so different? What united them was the determination between June 1941, when Hitler invaded the Soviet Union, and the end of the European war (by which time Roosevelt was dead) that Hitler's Reich should suffer total defeat and Nazism be extirpated. Everything else was problematic and contingent.The main purpose of Stalin's actions in East Europe at the end of the Second World War was simply a continuation of Russian policies since the 16th century, to expand as much as possible in all directions.  Russia had gained and then lost control of Lithuania, Estonia and Latvia, and of course had regained them during the war.  Russia had invaded and seized parts of Poland more than once, invaded Germany in 1914, and invaded Poland and the Balkan states (intending to invade Germany again) during the 1918-1919 period, just after the Revolution.  British and French troops helped the Poles and Balkans drive them out