Immediately after its creation, the MSA operated the second-hand ships of the former Japanese Navy, but it was only allowed to use smaller and slower vessels. The designations of PL, PM, PS and PC were used to classify ships as being: Patrol Ship – Large, Medium, Small and "Craft" = very small. From FY1949 the construction of new ships began. Because GHQ instructed the service to model its ships after those of the USCG, the 700-ton PL "Daiou"-class was based on "Cactus"-class buoy tenders, the 450-ton PM "Awaji"-class patrol vessel was based on "Thetis"-class patrol boats, the 270-ton PS "Kuma"-class patrol vessel was based on "Active"-class patrol boats, and the 23-meter PC "Hatsunami"-class patrol craft used a USCG 75-foot patrol boat as a model. However, these copies of American ship types were found wanting as they neither suited the actual operational work of the MSA nor the sea conditions around Japan.