Early flights of vertical start and landing machines are almost as old as aviation itself, but the first helicopters in the modern sense of the word, used in the military, were Nazi German Fl 282 Kolibri and Fa 223 Drache. They were soon followed by Americans with Sikorsky's S-4, and, after the WW II, Bell 47. Those first helicopters were used mainly for observation and medevac. It was not until Vietnam War when new, larger, more robust and heavily armed helicopters formed a separate branch of warfare, with attack, transport and recon machines closely working with infantry and special forces. A group of helicopters could fly to any place, secure it and prepare their base of operations there; in the case of heavy resistance, they could move to another location. US experiences were picked up and further built on by Russians, who introduced their Mi-24 in 1972. Mi-24 combined armoured frame with heavy weaponry and ability to transport a squad of soldiers, which made it a truly universal tool of mobile warfare. In 1991 Gulf War, a squadron of four American AH-64s in half an hour obliterated around 100 Iraqui tanks and armoured vehicles while suffering only minor damage themselves, proving that Gunships are a force to be reckoned with.