Intelligence sharing refers to the formal or informal transfer of classified information — including surveillance data, satellite imagery, signals intercepts, and human intelligence — between governments, military commands, or intelligence agencies. Allied intelligence sharing, such as through the Five Eyes partnership (U.S., UK, Canada, Australia, New Zealand), is a foundation of Western collective security. Adversarial intelligence sharing, such as Russia providing Iran with the locations of U.S. military assets, is a form of indirect warfare that can directly affect the outcome of military operations and the survival of troops in the field without constituting a formal declaration of war.