The Wikipedia article of the day for July 12, 2017 is Battle of Prokhorovka.
The Battle of Prokhorovka (12 July 1943), one of the largest tank battles in history, was fought between Waffen-SS units of Nazi Germany and Red Army units of the Soviet Union during the Second World War on the Eastern Front. The climax of the German offensive Operation Citadel, it resulted when the Soviet 5th Guards Tank Army intercepted the II SS-Panzer Corps of the German Wehrmacht near Prokhorovka. The Soviet forces were decimated in the attack, but succeeded in preventing the Wehrmacht from capturing Prokhorovka and breaking through the last heavily fortified defensive belt. With the Germans unable to accomplish their objective for Operation Citadel, they cancelled it and began redeploying their forces to deal with new pressing developments elsewhere. The failure of the operation marked the first time in the war that a major German offensive was halted before it could break through enemy defences. The Soviet Union permanently gained the strategic initiative, and Germany permanently lost the capacity to launch offensives of this scale on the Eastern Front.