World War II: Key Phases and Military Campaigns (1939-1945)

1. Blitzkrieg: The Era of Swift Action (1939–1940)

The first phase of the war was characterized by the uninterrupted advance of the German armies, employing a tactic known as Blitzkrieg (swift action). This strategy relied on the use of highly mobile units aimed at breaking the enemy's front and destroying the main points of defense. This tactic was successfully utilized in four major offensives:

• September 1939: Invasion of Poland
• April 1940: Occupation of Norway and Denmark
• May 1940: Invasion of the Netherlands, Belgium, and Luxembourg
• June 1940: Start of the invasion of France

The invasion of Poland was not complete because the Russians quickly invaded the east, necessitating a German-Russian agreement to divide the Polish territory. The Russians subsequently occupied Estonia, Latvia, Lithuania, and territories in Romania.

The invasion of France had a double consequence:

1. The division of France into two parts:
   • The German-dominated West.
   • The South/East, governed by the new pro-Nazi Vichy regime.
2. The mobilization of Italy alongside Germany.

2. The Conversion into a World Conflict (1940–1941)

After a new attempt at a swift war failed (the Battle of Britain), new fronts opened up in the conflict:

• Mediterranean Front

  The Italians attacked Greece in 1940 (an ally of the United Kingdom) and Egypt (under British rule). The failure in both cases was rectified by the counteroffensive led by Marshal Rommel in Libya and the subsequent occupation of Yugoslavia, Greece, and Crete.

• Russian Front

  Opened by the Germans in June 1941, thus breaking the non-aggression pact that united the two countries. The Germans advanced eastward continuously until December.

• Pacific Front

  Opened by the Japanese in December 1941 with a surprise bombing of the American base at Pearl Harbor, which caused the United States to break the neutrality it had held until then. The Japanese invaded Southeast Asia and the islands of Oceania. In response, the United States secured declarations of war against the Axis from most Latin American states in 1941, except for Argentina, which joined the Allies in 1945.

3. The Turning Point and Allied Triumph (1942–1945)

By 1942, the Allies had managed to stop the armies of the Axis on all fronts, and starting in 1943, the Allied advance became widespread:

• The Russians, between 1942 and 1943, liberated their territory from German troops and subsequently advanced into the Balkans in 1944.
• British and U.S. forces expelled the Germans from North Africa. They then invaded Italy and opened a new front in the Atlantic where the Normandy landings occurred, leading to the liberation of France, Belgium, and the Netherlands.
• In the Pacific, the U.S. expelled the Japanese from the Philippines.

In 1945, at the Yalta Conference, Stalin, Roosevelt, and Churchill agreed to a coordinated action of the three armies, which culminated in the end of the war in Europe.

The Japanese tried to continue fighting, but were deterred by the atomic bombs dropped on Hiroshima and Nagasaki in August 1945.