From the 1950s to 1975, the Navy had three types of fast task force escorts and one type of convoy escort. The task force escorts were cruisers (CAG/CLG/CG), frigates or destroyer-leaders (DL/DLG), and destroyers (DD/DDG); the convoy escorts were ocean escorts (DE/DEG), often known as destroyer escorts. Added in the early 1970s was a new ocean escort called the patrol frigate (PF). In 1975, these classifications were simplified to cruiser (CG), destroyer (DD/DDG), and frigate (FF/FFG).