Book excerpt: The first aircraft to be purposely designed as a radar-equipped nightfighter, Northrop's P-61 Black Widow was heavily influenced by early RAF combat experience with radar-equipped aircraft in 1940/41. Built essentially around the bulky Radiation Laboratory SCR-720 radar, which was mounted in the aircraft's nose, the P-61 proved to be the largest fighter ever produced for frontline service by the USAAF. Twin-engined and twin-boomed, the Black Widow was armed with a dorsal barbette of four 0.50-in Browning machine guns and two ventrally-mounted 20 mm cannon. This volume features all the frontline users of the mighty P-61, and includes many first-hand accounts from pilots and gunners who saw action in the Pacific, Mediterranean and Western Europe.