Strategic bombing, involving medium- to long-range targets, began to appear among military organizations during World War II. Several types of aircraft have been developed over the years in the US and Russia specifically to specialize in dropping a significant amount of weaponry from the air. These planes differ from fighter bombers in that they do not operate in air-to-air attacks during combat; however, they can be used in tactical bombing missions. As several innovations have continued with aircraft development, strategic bombers have become even more feared with the introduction of stealth technology.