:)
at this 1943 conference, roosevelt, churchill, and stalin developed a strategic plan to defeat nazi germany and her allies.
a) the yalta conference
b) the atlantic charter
c) the tehran conference
d) the potsdam conference

It would be at the "Tehran Conference" in 1943 that Roosevelt, Churchill, and Stalin developed a strategic plan to defeat Nazi Germany and her allies, since it was becoming clear that the Germans were on the defensive at this point.