what is the term for a short statement about history that has not yet been
proved?

The answer would be claim. Unlike statement, claim can not be proven and it is not based on factual data. Claim is left for other people to decide if it is right or wrong. Usually, a country who lost the war will claim that they actually are the winners but there are not enough facts to prove it. Hope this helps :)

“destroyers for bases agreement in the destroyers for bases agreement between the united states and the united kingdom on september 2, 1940, fifty caldwell , wickes, and clemson class us navy destroyers were transferred to the toyalbnavy from the united states navy in exchange for land rights on british possessions.” i hope this you .