Air power refers to the use of aviation by nations and other political actors in the pursuit of power and security interests, along with the use of long-range missiles. Since armies and navies first began to experiment with the use of airplanes as implements of war, air power has emerged as an integral component of modern warfare. Air power was born in the crucible of World War I, but came of age in the conflagration of World War II. The developmental history of air power is significant to security studies in general and to the study of air power in particular. Owing to the rapid series of state changes in air power, trying to understand the nature of air power and its effects on modern warfare and international security has become more complicated. Two questions that are central to the study of international security are whether air power facilitates offense as a whole and whether it encourages aggression as a result. There has also been a debate over the issue of how air power can most effectively be used to coerce an enemy through strategic bombing. Another source of disagreement is the question of whether air and space power constitute one subject or two. In general, there are compelling merits in treating space power as a domain of national security theory and policy separate from those of land, sea, and air power.