Challenges to Security in Space was first published in early 2019 to address the main threats to the array ofU.S. space capabilities, and examine space and counterspace strategies and systems pursued primarily byChina and Russia and, to a lesser extent, by North Korea and Iran. This second edition builds on that work andprovides an updated, unclassified overview of the threats to U.S. space capabilities, particularly from Chinaand Russia, as those threats continue to expand.