They closely coordinated Operation Bagration that destroyed the German Army Group Center, the largest German army group in Russia, with Operation Overlord, launching Bagration about six days after Overlord was launched. We grabbed the Germans by the nose while the Russians kicked them in the behind, enabling both of us to win in about 11 months after both offensives were started. Good idea to join the celebration.
We finished off the Germans, but Britain and USSR had been fighting them for years already by the time we got into it.