The character of war is changing. The revolutionary nature of the onset of artificial intelligence threatens to make current defense strategies obsolete. This is particularly relevant in the impact on military activities in the upper levels of the earth’s atmosphere. 

High-altitude platforms are important in the strategic shift in military technology development and acquisitions. Operating in the stratosphere above all other aircraft, high-altitude platforms provide critical battlefield connectivity and intelligence, surveillance and reconnaissance (ISR) over great distances.

This white paper provides a short history of the militarisation of the stratosphere and great power competition, tracking key developments from the 1990s until the present. It also analyses the military significance of the two main classes of high-altitude UAVs: High-Altitude Long-Endurance (HALE) and High-Altitude Platform Station (HAPS) platforms.