CAC
The Common Access Card (CAC) is a United States Department of Defense smartcard issued as standard identification for active duty military personnel, selected reserve personnel, civilian employees, and eligible contractor personnel.

The CAC is used as a general identification card as well as for authentication to enable access to DoD computers, networks, and certain DoD facilities. It also serves as an identification card under the Geneva Conventions. The CAC enables encrypting and crytographically signing email, facilitating the use of PKI authentication tools, and establishes an authoritative process for the use of identity credentials.

Sir, you need to show your CAC to gain entry to the base.