From under the debris "Ivans" rose up to decimate passing German patrols. The constant artillery bombardment and air strikes from both sides, meager supply lines, and onset of the Russian winter (–30°F) led to hellish conditions for everyone. The air in command bunkers became almost too stale to support life. Russian soldiers fought for days with only a piece of bread and insufficient, polluted water for rations. German soldiers, poorly equipped for the extreme winter, froze to death, lost limbs to frostbite, were tormented by fleas and lice, and were gnawed by rats. Both armies ignored Geneva Convention requirements, and prisoners, especially the wounded, were murdered, starved, or left out in the cold to die. Desertions and defections were rampant on both sides despite summary executions of anyone caught trying to leave by waiting German SS and Russian NKVD cadres. The German commander, Field Marshall Friedrich Paulus, surrendered as his command position was finally overrun. While the conflict ended, horror and cruelty continued. The emaciated German survivors froze, starved, and died on "death marches" and in unsheltered prisoner of war camps (which easily matched the barbarous conditions and treatment inflicted by the Germans on Russian prisoners of war). Many of the freed Russian prisoners were executed by the NKVD for the "treason" of allowing themselves to be captured.