Short answers, pulled from the story.
The Second Battle of Kharkov was a 1942 battle in the Eastern Front of World War II where Soviet forces launched an offensive that ended in a major defeat. The Red Army attacked German positions near Kharkov starting on the 12th of May 1942 but suffered heavy losses and encirclement by mid-May.
Marshal Semyon Timoshenko and Lieutenant General Kirill Moskalenko commanded the Soviet forces during the Second Battle of Kharkov. Stalin ordered the offensives despite warnings from advisors like General Boris Shaposhnikov and General Aleksandr Vasilevsky about the risks involved.
The Second Battle of Kharkov began at 6:30 a.m. on the 12th of May 1942 and concluded with the collapse of Soviet forces by the end of May 1942. Major fighting continued through the 25th of May when Soviet attempts to break the encirclement failed completely.
Estimates for the Second Battle of Kharkov indicate over 277,190 total Soviet casualties including 75,000 killed and 239,000 taken prisoner. German casualties were significantly lower with most estimates placing dead wounded or missing figures around 20,000 men.
The Second Battle of Kharkov failed because Joseph Stalin underestimated German military power and ignored advice to organize a strong defense in the southwestern sector. Poor reconnaissance intelligence gathering and the inability to stage offensives properly led to Soviet forces being surrounded and destroyed.