In Brief:Tarzan's Triumph (1943)

Jane is in London, so boy and Tarzan must take on a group of Nazi's who invade the jungle, and more importantly a hidden city where a friend of Tarzan lives.

Its war time action and daring do as Tarzan refuses to get involved until his family and friends are put under the gun by the bad guy Nazi's. Its over done and a great deal of fun with several bits that must have brought cheers (Tarzan go to War Now) and laughs (the final fade out).

Its clear its no longer MGM, this was the first film for the ten or so year long run at RKO, but the film is still a blast as Tarzan and company hit all the right notes (and I don't think we hear the Tarzan yell at any point.)