12 × 16-inch (406 mm)/50 cal. Mark 7 guns
20 × 5-inch (127 mm)/38 cal. Mark 12 guns
96 × 40 mm/56 cal. Bofors
72 × 20 mm/70 cal. Oerlikon

The Montana-class battleships of the United States Navy were planned as successors to the Iowa class, being slower but larger, better armored, and having superior firepower. Five were approved for construction during World War II, but changes in wartime building priorities resulted in their cancellation in favor of the Essex-class aircraft carriers and Iowa class before any Montana-class keels were laid. With beams of 121 feet, they would have been the first U.S. battleships as originally designed to be too wide to transit the 110-foot-wide locks of the Panama Canal.


Intended armament would have been 12 16-inch (406 mm) Mark 7 guns in four triple turrets, up from the Iowas' three triple 16s. With an increased anti-aircraft capability and thicker armor belt, the Montana class would have been the largest, best-protected, and most heavily armed U.S. battleships ever, the only class to come close to rivaling the Empire of Japan's immense Yamato-class battleships.^[7]


Preliminary design work for the Montana class began before the US entry into World War II. The first two vessels were approved by Congress in 1939 following the passage of the Second Vinson Act. The Japaneseattack on Pearl Harbor delayed construction of the Montana class. The success of carrier combat at the Battle of the Coral Sea and, to a greater extent, the Battle of Midway, diminished the value of the battleship. Consequently, the US Navy chose to cancel the Montana class in favor of more urgently needed aircraft carriers, amphibious and anti-submarine vessels.^[8]


Because the Iowas were fast enough to escort the new Essex-class aircraft carriers, their orders were retained,^[9] making them the last US Navy battleships to be commissioned.