> No nation ever started building a battleship in the time of war that then saw service in that war. Battleships commissioned during war had been started during peacetime or they were scrapped during the war because they didn't fit into the time or they were started under high holds, but they couldn't be finished in time. aircraft carriers are likely to be the same place going forward - you have to make them beforehand.
The first Iowa-class battleships were laid down in 1940 (so after WW2 started but before the US entered the war), and did see active service in the war. The British had two classes of battlecruisers that were laid down in WW1 that saw service in WW1, although they commissioned after the Battle of Jutland, which was essentially the only major naval action of WW1. It's debatable if you want to lump battlecruisers in with battleships, but considering that the main long-lead item of battleships are their guns and battlecruisers are essentially battleship guns on a cruiser, I think it's fair to do that here.
Aircraft carriers are not battleships, but I do think it is worth noting that except for Essex herself, all of the Essex carriers were laid down after the US entry in WW2 and these were the ships that formed the US assault in the Pacific in WW2.
The first Iowa-class battleships were laid down in 1940 (so after WW2 started but before the US entered the war), and did see active service in the war. The British had two classes of battlecruisers that were laid down in WW1 that saw service in WW1, although they commissioned after the Battle of Jutland, which was essentially the only major naval action of WW1. It's debatable if you want to lump battlecruisers in with battleships, but considering that the main long-lead item of battleships are their guns and battlecruisers are essentially battleship guns on a cruiser, I think it's fair to do that here.
Aircraft carriers are not battleships, but I do think it is worth noting that except for Essex herself, all of the Essex carriers were laid down after the US entry in WW2 and these were the ships that formed the US assault in the Pacific in WW2.