In July of 1940 the US Congress authorized their "Two-ocean Navy" construction program and among the ships to be built were five super-battleships in the 58,000-ton range that had been design-studied a few years earlier. Because of her great size, this class would not be able to steam at the 45,000-ton Iowa-class' 33 knots, but at the more sedately 28-30 knots of the South Dakota-class. The extra tonnage (over the Iowa-class) was mainly used up in mounting a fourth heavy turret, and a double armor belt somewhat like Yamato. A broad beam deliberately too wide for the Panama Canal was a first for American warship construction, but the trade-off was the lesser chance of sinking in an engagement due to her great size. None of these ships were started due to more urgent repair and construction needs in shipyards at the time. By the time the Montana-class could be readied for construction it became obvious that carriers were the "capital ships" now needed in naval warfare, and the orders for five Midway-class CV's replaced those for the Montanas.

In "Grand Fleet", the American naval buildup comes earlier, and two of these giants, Montana and New Hampshire, join the Atlantic and Pacific fleets, respectively, as fleet flagships in mid-1943. The Iowas are being built at the same time in different shipyards and are 'competing' to see which can be finished first. Montana wins by a small margin. A longer, Iowa-style bow is put on her to help weather the heavy seas of the North Atlantic and to gain an extra knot of speed. The boat deck designed to be between the funnels is stuffed with AA guns instead. The DP guns, contrary to the initial design, are sited higher (like Iowa) but use a two-up/three down pattern instead of the Iowas' three-up/two down. The results are the most powerful Allied gunships in the world, a match for all foreign designs except perhaps the Führer and the zenith of battleship configuration and construction. The US Navy had not one but FIVE under construction. The designation given to battleships that exceeded the 45,000-ton limit of the last Treaty (BBB) was applied to Montana as the first American warship to do so. Modern naval warfare had changed, though, and the pressing need for aircraft carriers saw two of the class completely converted at an early stage into the Midway-class CVB's, and one interesting hybrid that had both big guns AND flightdeck.

Montana's maiden war cruise was an uneventful escort of a Arkangelsk-bound convoy. Not long after that, the "Last Great Sortie" by the surface forces of the Kriegsmarine was at hand. Battleships Montana, Massachusetts, Saint Andrew and Duke of York, the "A" team of Allied gunships, was on an interception course to prevent German battlewagons from cutting off a convoy leaving Iceland for Russia. In the North Sea the opposing forces met, and a huge maelstrom of smoke and gunflash began. Every Allied ship concentrated on the lead German ship and the "Big Sky" battleship's second salvo knocked a huge piece of Führer's upperworks onto her "Caesar" turret, putting it out of action. Führer deftly ranged in on Montana and massive 21" shells hit home on the third salvo. Three rapid-fire detonations split the air like a thunderclap, and Montana from forecastle to fantail simply disappeared, leaving a big piece of sky where the ship had been.

New Hampshire went to the Pacific around the Horn and joined the Central Pacific drive to the Japanese homeland. Off the Bonin Islands shelling vital staging airfields whilst the Leyte Gulf battles raged, the New Hampshire missed the opportunity to pit herself against the giant Japanese Satsuma and Yokozuna off the Philippines. Returning after the War to celebrate Navy Day on the East Coast, the New Hampshire lost power to her turbines in a fast-moving hurricane that drove her onto the rocks next to the hulk of an old four-masted sailing ship. The storm surge had put New Hampshire so far up on Hampton Beach that she could not be returned to the sea. Unable to keep up with the fast carrier groups, and somewhat superfluous in the Post-War navy, the New Hampshire was scrapped slowly, in place, looking like a beached whale whose bones were being picked clean.