Question: What is the other name  for a huge area of heavy fighting across Europe with the Soviet Union having occupied and annexed several countries effectively handed over by Nazi Germany?

Context paragraphs:
Military occupations by the Soviet Union: During World War II, the Soviet Union occupied and annexed several countries effectively handed over by Nazi Germany in the secret protocol Molotov–Ribbentrop Pact of 1939.  These included Eastern Poland (incorporated into two different SSRs), as well as Latvia (became Latvian SSR), Estonia (became Estonian SSR), Lithuania (became Lithuanian SSR), part of eastern Finland (became Karelo-Finnish SSR) and eastern Romania (became the Moldavian SSR and part of Ukrainian SSR).  Apart from Molotov–Ribbentrop Pact and post-war division of Germany, USSR also occupied and annexed Carpathian Ruthenia from Czechoslovakia in 1945 (became part of Ukrainian SSR).

German–Soviet Border and Commercial Agreement: The German–Soviet Border and Commercial Agreement, signed on January 10, 1941, was a broad agreement settling border disputes and continuing raw materials and war machine trade between the Soviet Union and Nazi Germany.  The agreement continued the countries' relationship that started in 1939 with the Molotov-Ribbentrop Pact containing secret protocols dividing Eastern Europe between the Soviet Union and Germany, and the subsequent invasions by Germany and the Soviet Union of that territory.  The "German–Soviet Border and Commercial Agreement" contained additional secret protocols settling a dispute regarding land in Lithuania previously split between the countries.  The agreement continued Nazi-Soviet economic relations that had been expanded by the 1939 German–Soviet Commercial Agreement and the larger 1940 German–Soviet Commercial Agreement.

German–Soviet Frontier Treaty: The German-Soviet Frontier Treaty was a second supplementary protocol, of the 1939 Hitler-Stalin Pact (known as the "German-Soviet Treaty of Nonaggression", or by its original name of the "German–Soviet Treaty of Friendship, Cooperation and Demarcation").  It was a secret clause as amended on September 28, 1939 by Nazi Germany and the Soviet Union after their joint invasion and occupation of sovereign Poland.  It was signed by Joachim von Ribbentrop and Vyacheslav Molotov, the foreign ministers of Germany and the Soviet Union respectively, in the presence of Joseph Stalin.  The treaty was a follow-up to the first secret protocol of the Molotov–Ribbentrop Pact signed on August 23, 1939 between the two countries prior to their invasion of Poland and the start of World War II in Europe.  Only a small portion of the protocol which superseded the first treaty was publicly announced while the spheres of influence of Nazi Germany and the Soviet Union remained classified.  The third secret protocol of the Pact was signed on January 10, 1941 by Friedrich Werner von Schulenberg, and Molotov, whereas Germany renounced its claims to portions of Lithuania, only a few months before their anti-Soviet Operation Barbarossa.

Nazi–Soviet economic relations (1934–41): After the Nazis rose to power in Germany in 1933, relations between Germany and the Soviet Union began to deteriorate rapidly, and trade between the two countries decreased.  Following several years of high tension and rivalry, Nazi Germany and the Soviet Union began to improve relations in 1939.  In August of that year, the countries expanded their economic relationship by entering into a commercial agreement whereby the Soviet Union sent critical raw materials to Germany in exchange for weapons, military technology and civilian machinery.  That deal accompanied the Molotov–Ribbentrop Pact, which contained secret protocols dividing central Europe between them, after which both Germany and the Soviet Union invaded countries listed within their "spheres of influence".

Military history of the Soviet Union: The military history of the Soviet Union began in the days following the 1917 October Revolution that brought the Bolsheviks to power.  In 1918 the new government formed the Red Army, which then defeated its various internal enemies in the Russian Civil War of 1917–22.  The years 1918–21 saw defeats for the Red Army in the Polish–Soviet War (1919–21) and in independence wars for Estonia (1918–20), Latvia (1918–20) and Lithuania (1918–19).  The Red Army invaded Finland (November 1939); fought the Battles of Khalkhin Gol of May-September 1939 (together with its ally Mongolia) against Japan and its client state Manchukuo; it was deployed when the Soviet Union, in agreement with Nazi Germany, took part in the invasion of Poland in September 1939, and occupied the Baltic States (June 1940), Bessarabia (June–July 1940) and Northern Bukovina (June–July 1940) (from Romania).  In World War II the Red Army became a major military force in the defeat of Nazi Germany and conquered Manchuria.  After the war, it occupied East Germany and many nations in central and eastern Europe, which became satellite states in the Soviet bloc.

Kurt Agricola: Kurt Wilhelm Albert Karl Agricola (15 August 1889 – 27 December 1955) was a general in the Wehrmacht of Nazi Germany during World War II who held senior level occupational rear-security commands in the occupied Soviet Union.  A native of Saxony, Agricola entered army service in 1908 and served during World War I.  During the interwar era, he held staff assignments and continued to rise through the army's ranks in the Wehrmacht of Nazi Germany.  His career ended stalled in January 1939, when he was sent into retirement on political grounds because of his marriage to Martha born Hahn, a Jewish woman.  Reactivated again upon the start of World War II, Agricola received exclusively positions behind the front line.  As rear area commander of the 2nd Army in the occupied Soviet union during 1941–43, Agricola brought changes in the Wehrmacht's harsh occupation policies and was successful in maintaining control of his area of occupied territory from Soviet partisans.  Shortly after the war's end, he was arrested by Soviet authorities, convicted of war crimes and remained in captivity for a decade.  One of the last German prisoners in the Soviet Union, he was released in October 1955 and died shortly thereafter in West Germany.

European theatre of World War II: The European theatre of World War II, also known as the Second European War, was a huge area of heavy fighting across Europe, from Germany's and the Soviet Union's joint invasion of Poland in September 1939 until the end of the war with the Soviet Union conquering much of Europe along with the German unconditional surrender on May 8, 1945 (Victory in Europe Day).  The Allied forces fought the Axis powers on two major fronts (the Eastern Front and Western Front) as well as in the adjoining Mediterranean and Middle East theatre.

General Government: The General Government (German: "Generalgouvernement" , Polish: "Generalne Gubernatorstwo" , Ukrainian: Генеральна губернія ), also referred to as the General Governorate, was a German zone of occupation established after the joint invasion of Poland by Nazi Germany and the Soviet Union in 1939 at the onset of World War II.  The newly occupied Second Polish Republic was split into three zones: the General Government in its centre, Polish areas annexed by Nazi Germany in the west, and Polish areas annexed by the Soviet Union in the east.  The territory was expanded substantially in 1941 to include the new District of Galicia.

Allied-occupied Germany: Upon the defeat of Nazi Germany in World War II, the victorious Allied powers asserted their joint authority and sovereignty over 'Germany as a whole', defined as all territories of the former German Reich which lay west of the Oder–Neisse line; having declared the extinction of Nazi Germany at the death of Adolf Hitler (see 1945 Berlin Declaration).  The four powers divided 'Germany as a whole' into four occupation zones for administrative purposes, creating what became collectively known as Allied-occupied Germany (German: "Alliierten-besetztes Deutschland" ).  This division was ratified at the Potsdam Conference (17 July to 2 August 1945).  In autumn 1944 the United States, United Kingdom and Soviet Union had agreed on the zones by the London Protocol.  The powers at Potsdam approved the detachment from 'Germany as a whole' of the German eastern territories east of the Oder-Neisse line; with the exact line of the boundary to be determined at a final German Peace Treaty.  This treaty was expected to confirm the "shifting westward" of Poland's borders (back to approximately as they were before 1722), as the United Kingdom and the United States committed themselves to support there the permanent incorporation of former eastern German territories into Poland and the Soviet Union.  In the closing weeks of fighting in Europe, United States forces had pushed beyond the agreed boundaries for the future zones of occupation, in some places by as much as 200 mi .  The so-called line of contact between Soviet and American forces at the end of hostilities, mostly lying eastward of the July 1945-established inner German border was temporary.  After two months in which they had held areas that had been assigned to the Soviet zone, U.S. forces withdrew in the first days of July 1945.  Some have concluded that this was a crucial move that persuaded the Soviet Union to allow American, British and French forces into their designated sectors in Berlin, which occurred at roughly the same time (July 1945), although the need for intelligence gathering (see Operation Paperclip) may also have been a factor.

German–Soviet Credit Agreement (1939): The German–Soviet Credit Agreement (also referred to as the German–Soviet Trade and Credit Agreement) was an economic arrangement between the Soviet Union and Nazi Germany whereby Soviet Union received an acceptance credit of 200 million Reichsmark.  over 7 years with an effective interest rate of 4.5 percent.  The credit line was to be used during the next two years for purchase of capital goods (factory equipment, installations, machinery and machine tools, ships, vehicles, and other means of transport) in Germany and was to be paid off by means of Soviet material shipment from 1946 onwards.  The economic agreement was the first step toward improvement in relations between the Soviet Union and Germany.  The next day after the Credit Agreement, the Soviet Union went to war against Japan, in a successful four-week military campaign in the Far East.  The Nazi-Soviet Pact was signed four days after the Credit Agreement.  The 1939 German–Soviet Commercial Agreement renewed declined Nazi–Soviet economic relations and was adjusted and expanded with the larger German–Soviet Commercial Agreement in February 1940 and January 1941 German–Soviet Border and Commercial Agreement.  German shipments to the Soviets became tardy and failed to provide all that was promised the closer the date of Barbarossa came.  The Soviets fulfilled their obligations to the letter right up until the invasion, wanting to avoid provoking Germany.  All these agreements were terminated when Germany invaded the Soviet Union in June 1941, in violation of the treaties between the two countries.  Soviet trade with Germany in the pre-invasion period ended up providing the Germans with many of the resources they needed for their invasion of the Soviet Union.

Supporting paragraphs: European theatre of World War II Military occupations by the Soviet Union
Answer: Second European War