The Portland class of heavy cruisers was a class of ships designed and constructed by the United States Navy in 1930. The two ships of the class, and , saw extensive service during the Pacific War in World War II. Designed as a modification over the previous , the Portland class displaced just under and featured heavier armor and armament than previous cruisers. Featuring 8"/55 caliber guns and designed to function as fleet flagships, the Portland class were intended to fix problems with armament and armor that had been a weakness of preceding U.S. cruisers. These designs were carried over to the following , to which six intended Portland cruisers were converted, three of which were already mid-construction. Portland served in many engagements including the Battle of Coral Sea, the Battle of Midway and the Guadalcanal Campaign, where she was severely damaged but nonetheless able to return to service. She later fought in the Battle of Leyte Gulf and the Battle of Okinawa. Indianapolis served as a fleet flagship for much of the war and fought in the Battle of Philippine Sea and the Battle of Iwo Jima. On 30 July 1945, after transporting components for the nuclear weapons Little Boy and Fat Man from the United States, she was torpedoed by the . Due to a series of errors and miscommunications her loss was not discovered for several days, and only 316 of her 1,195 crew survived – the greatest single loss of life at sea, from a single ship, in the history of the U.S. Navy. Background The Portland class was the third class of heavy cruiser to be constructed by the United States Navy following the Washington Naval Treaty of 1922. The first "treaty cruisers" were the two of the ordered in 1926, which emphasized armament and speed at the expense of protection. These ships were followed by the six vessels of the Northampton class ordered in 1927 with slightly better armor, and introduced the configuration of three triple turrets which would become standard on U.S. Navy heavy cruisers. The Portland class was a modification of both the Pensacola and Northampton designs. Portland was the first ship constructed under the provision of the February 13, 1929 "Cruiser Act" of the United States Congress, which authorized one aircraft carrier and 15 "light cruisers" to be built. had been assigned the first hull number in this group, but was