I would like to point out that Great Britain had a jet-bomber in development in 1945 called the English Electric Canberra. Due to post-war cut-backs the first Canberra did not fly until May 1949, but it's not unreasonable to suggest that with war time spending the aircraft could have been flying much sooner. The first prototypes were in production in early '46 and the first flights proved the aircraft to be vice free - from prototype to service, the Canberra was extremely quick for a peace time development in post-war Great Britain.