 Complete the following phrase:  The U-2 became known as the aircraft used by the 588th Night Bomber Regiment, composed of an all-woman pilot and ground crew complement. The unit was notorious for daring low-altitude night raids on German rear-area positions. Veteran pilots Yekaterina Ryabova and Nadezhda Popova on one occasion flew eighteen missions in a single night. The women pilots observed that the enemy suffered a further degree of demoralization simply due to their antagonists being female. As such, the pilots earned the nickname Night Witches German Nachthexen, Russian Ночные ВедьмыNočnye Vedmy. The unit earned numerous Hero of the Soviet Union citations and dozens of Order of the Red Banner medals; most surviving pilots had flown nearly 1,000 combat missions by the end of the war and took part in the 