North Carolina was launched 13 June 1940 and was very close to commissioning (09 April 41) when the scheme apparently was first mentioned on 13 Feb 1941. Washington had been launched on 01 June 1940 and was similarly close to commissioning (15 May 1941), so at the time of the scheme was being mentioned the US had a good idea of when it's fast BB's would be coming online. It's also interesting that the Washington's first service was as part of the British Home Fleet (26 March 1942) even though the US was now at War with Japan and the threat, of the Kongos, was real not hypothetical, as it would have been in Feb. '41. That would make me doubt that the US would want the British BB as a counter to Kogo's. The Duke of York launched shortly prior to (28 Feb 1940) the time of the North Carolinas but wouldn't commission until November 1941, six months after the last North Carolina, the Washington, commissioned. I am sure that if such things were looked at, the approximate time the ship would be ready for service would be known. The South Dakota, the lead ship in the follow-on US BB class launched on 7 June 1941 and commissioned on 20 Mar '42, at the same time Washington was sent off to the Home Fleet. So the US apparently felt 2 fast BB's met it's immediate needs even though they were now actually at war with Japan and had lost 8 battleships, USS Arizona (BB-39), USS California (BB-44), USS Maryland (BB-46), USS Nevada (BB-36), USS Oklahoma (BB-37), USS Pennsylvania (BB-38), USS Tennessee (BB-43) and USS West Virginia (BB-48) either sunk and/or damaged. Massachussetts launched 23 September 41, Indiana launched 21 November 41, Alabama launched on 16 Feb. 42. So by the time the US would have had use of the Duke of York they would have had 5 fast BB's in the water, 2 of them commissioned. If the trade was based upon US needs real or perceived, I fail to see a good case made for it. The need of the UK for additional 8" cruisers to guard it's far flung merchant fleet is more obvious. In December 1941 over 70% of the US populace still opposed active participation in the European war. Even after Pearl Harbor was attacked and Roosevelt prepared to declare war on Japan, he was unsure of what political support he would have for involving the US in war in Europe. A speech asking for a Declaration of War against Japan and Germany was actually prepared but he decided against using it, because he was unsure if it would pass and asked for a DOW against Japan alone. This and other factors make me lean towards a hypothesis along the lines of what Carronade proposed and the scheme was a way to get Britain the help she needed without Roosevelt taking a political hit.