The Vietnam War was the first conflict in which helicopters were used in large numbers. However, the helicopters used were, besides the Bell AH-1G "Cobra", only transport and reconnaissance helicopters, which were not developed for combat and only lightly armed. The United States lost over 5,000 helicopters and that in a war in that the enemy was as large as in a conventional battle in World War II, for example. Not only that, because of the tropical climate and the high temperature and humidity, the highly stressed components corroded much faster.