The U.S. Navy was the last of the major naval powers to initiate heavy cruiser construction under the terms of the Treaty; because of this it had the advantage of surveying the development of contemporary vessels under construction around the world. The U.S. Navy began its heavy cruiser construction program in the 1930s, and when the war in Europe began in 1939 it had 18 heavy "treaty cruisers", the British 15, the Japanese 12, the French 7, the Italians 7, and the Germans 2.
Almost from the first, there was certain dissatisfaction with the very limited protection of the 8-inch gun cruiser. As it became evident that more weight was available than had originally been estimated, protection was improved as much as possible in the ships still under construction. Initially planned as Northampton class ships, two ships were built to a modified design with a modified superstructure and minor improvements. These became the Portland class. The Portland Class, originally slated as CA 32-36, was in effect an upgraded version of the Northampton Class cruisers. In the event, only two units were built to this design, with
The follow on group to the Portland Class cruisers, CA 37-41, exhibited such superior characteristics, that an attempt was made to reorder CA 32-36 to its specifications. However, two ships, the Portland and the Indianapolis had been awarded to private builders and contract changes would be far too expensive. The remaining three ships were all at Navy yards and could be modified without great expense. Thus the Portland Class was relegated to just two ships, while CA 37 became the lead ship for the new New Orleans Class cruisers.
They Portland Class commissioned in 1932-33. The first Portland Class cruiser launched was the USS Indianapolis, on 7 November, 1931. She had a design full load displacement of 11,574 tons, a speed of 32.5 knots and an endurance range of 10,000 nm at 15 knots. Her main battery consisted of nine 8-in/55 guns and an anti-aircraft battery of eight 5-in/25 guns and eight 0.50 caliber machine guns. She actually came in heavy at a full load delivery displacement of 12,755 tons.
Treaty strictures limited "heavy" cruisers to ten thousand tons of displacement. (The treaty categorized warships by displacement--and armament.) To save displacement weight, Indianapolis was designed and built without much of the usual extra thick, heavy, armor plating--from above the plimsol line and covering a good portion of the bottom toward the keel- extending almost the full length of the ship ordinarily employed on capital ships of the line, as protection from mines and torpedoes. Indianapolis's armor, while inches thin, covered only her vital machinery spaces. While she was more vulnerable, she was also capable of great speed.
She was 610 feet, 3 inches in length, and 66 feet 1 inch at the beam, (widest point). She drew 17 feet 6 inches of draft. (24 feet when fully armed, manned and provisioned). Her design flank speed was 32 knots. She was equipped with eight White-Forster boilers located amidship, driving four Parsons geared turbines. Total horsepower was rated at 107,000 delivered through four screws. Her armament consisted of nine 8-inch guns placed in three turrets; two fore and one aft. Additionally there were four 5-inch guns, twenty-four 40mm intermediate range guns and thirty-two 20mm Oerlikon guns; the latter being installed during several overhauls and refits accomplished during the war.
On May 1, 1945, the USS Indianapolis had entered the Navy Yard, Mare Island, California, to get heavy underwater damage repaired from a Kamikaze Japanese suicide aircraft hit that she took in the Battle of Okinawa on 30 March 1945. Her overhaul was completed and she was reported ready for sea on July 16, 1945. Although all preparations had been made to give the vessel a post-repair shakedown period in San Diego, California, preparatory to her rejoining the Fleet in the combat area, assignment to a mission of greater importance necessitated the postponement of this period of refresher training until a later date. While in the Navy Yard, there had been a great number of changes among the officers attached to the vessel and a turnover in her enlisted complement in excess of 25 percent. Every advantage was taken of opportunities to send both officers and enlisted men to schools and other instruction, while in the Navy Yard; and when reported ready for sea, the ship was well organized and the training of personnel was progressing satisfactorily.
The Indianapolis proceeded unescorted at high speed from San Francisco to Pearl Harbor, thence to Tinian, where special cargo (atomic bomb parts) was landed. A great many passengers were transported to Pearl Harbor and a lesser number beyond that point. These factors interfered somewhat with the schedule of training under way, but instruction was continued, general drills were held daily and at least one battle problem was held during this passage.
Upon completion of unloading at Tinian, the Indianapolis was ordered by the Commander in Chief, Pacific Fleet to proceed to Guam. The route over which the Indianapolis was to travel, which was the only direct route between Guam and Leyte, and was the route regularly assigned vessels making passage between these islands, was considered within the acceptable risk limit for combatant vessels. At the time of the sailing of the Indianapolis, there was a shortage in this regard and escorts were, as a rule, not given combatant vessels which were capable of "taking care of themselves." The Indianapolis was considered to be in this class and escort, if furnished her, would have been at the expense of other requirements of greater urgency.
Early in the morning, at 12:15 A.M., on July 30, while the Indianapolis was steaming unescorted, and not zigzagging, at a speed of 17 knots through the water, under good conditions of visibility and in a moderate sea, two heavy explosions occurred against her starboard side forward, as a result of which explosions the ship capsized and sank between 12:27 and 12:30 A.M., July 30. The ship sank 12 minutes after the torpedoes hit. The Indianapolis was torpedoed and sunk by a Japanese submarine. Only 316 of the 1,196 crewmen were rescued. Orders to abandon ship were given by some officers locally, but general word to that effect was not passed throughout the ship. This was partly due to the disruption of all mechanical and electrical means of communication. Many men stood by their abandon ship stations until they were forced by the listing of the ship to enter the water. Much lifesaving equipment went down with the ship.
Aircraft patrols which daily covered a great part of the route followed by the Indianapolis, and which were sighted daily by the suriviors, failed to sight the oil slick or the survivors for two days after the sinking. Discovery of the survivors by aircraft patrol was largely accidental.
The Portland was decommissioned in 1946 and laid up in reserve. A modernization was considered in 1952 but dismissed and she was stricken 1 March 1959 and scrapped.
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