The United States Coast Guard (USCG) is a branch of the United States Armed Forces responsible for enforcing maritime law and providing search and rescue operations. The USCG rank system consists of four main categories: CAPT (4 letters), ENS (3 letters), CPO (3 letters), and PO (2 letters). CAPT stands for Captain, the highest rank in the USCG, and is typically held by officers with at least 20 years of service. ENS stands for Ensign, the second-highest rank in the USCG, and is typically held by officers with at least two years of service. CPO stands for Chief Petty Officer, the third-highest rank in the USCG, and is typically held by enlisted personnel with at least eight years of service. PO stands for Petty Officer, the fourth-highest rank in the USCG, and is typically held by enlisted personnel with at least two years of service.