The United States began employing drones shortly after 9/11 for executing "high-value targets" within the secret confines of an extra-judicial targeted-killing program. The program started slowly, but as the U.S. public seemed to accept these remotely- controlled unmanned bombings, the program escalated under Bush, followed by Obama to the point it was being used globally as a strategic counter-terrorism tool. The use of this policy became globally controversial and many questioned the tactics, transparency, objectives, and outcomes.