World War II: German forces begin a massive offensive against the Soviet Union at the Battle of Kursk, also known as Operation Citadel.

The Soviet Union, officially the Union of Soviet Socialist Republics (USSR), was a transcontinental country that spanned much of Eurasia from its formation in 1922 until its dissolution in 1991. It was the world's third-most populous country, the largest by area, and bordered twelve other…