The use of airplanes in warfare began in earnest during World War I. By the end of World War II, the use of fighter aircraft and bombers was commonplace and the importance of air warfare continued to grow, as did the importance of effective anti-aircraft defenses. During the 1950s, the refinement of rocket technology allowed for the construction of compact missiles which were used to deliver explosive warheads to targets swiftly and accurately. Batteries of surface-to-air missiles, or SAMs, were built to protect cities and ground installations against airborne attacks. The long range and high accuracy of SAM Missile Batteries provided a much more effective defense than the anti-aircraft guns of World War II.