World War I. The idiom "The balloon's going up!" as an expression for impending battle is derived from the very fact that an observation balloon's ascent likely signaled a preparatory bombardment for an offensive. World War II Barrage balloons, widely known as "blimps," were used by the United Kingdom to intercept air attacks by German bombers and V-1 cruise missiles. Japan used recently discovered high-altitude air currents to send fire balloons (or Fu-Go balloon bomb) carrying explosive payloads to the United States. About 300 made it across the Pacific, causing some property damage and at least six deaths. The US government called for a press blackout on all balloon incidents, fearing what might happen if the Japanese started using fu-go to deliver biological weapons. Britain used free balloons in a number of ways including Operation Outward which launched nearly 100,000 small balloons to drop incendiaries on German occupied Europe or to trail wires to short out electrical distribution cables. Balloons also were used at sea, particularly by the US Navy for anti-submarine work. The Red Army of the Soviet Union used Observation Balloons for artillery spotting. 8 "Aeronautical Sections" existed and 19,985 observation flights were performed by balloonists of the Red Army during the war, clocking up 20,126 flight hours. 110 Soviet Observation Balloons were lost. Postwar The US military developed high-altitude ballooning programs for nuclear detection and surveillance, such as Project Mogul (linked to the Roswell Incident), Project Genetrix and Project Moby Dick. They also worked on the E77 balloon bomb, refining the principles of the Japanese fire balloon explosive-delivery system. Genetrix in particular was a program run by the U.S. Air Force, Navy, and the Central Intelligence Agency during the 1950s. Disguised as meteorological research, it launched hundreds of surveillance balloons that flew over China, Eastern Europe, and the Soviet Union to take photographs and collect intelligence. The balloons were manufactured by the aeronautical division of General Mills. They were about 20 stories tall, carried cameras and other electronic equipment, and reached altitudes ranging from 30,000 to over 60,000 feet, well above the reach of any contemporary fighter plane. Many balloons were blown off course or shot down by Soviet air defense. The overflights also drew protests from the target countries, while the United States defended its action. To increase effectiveness and minimize diplomatic blowback, it replaced the balloons with the newly developed U-2 reconnaissance plane, which was