In 1942, Nazi planners are considering a bold and daring plan--abducting Franklin Roosevelt from Camp David retreat.
In early 1943, the Abwehr becomes aware of a May meeting planned between Roosevelt and Churchill at Camp David. The opportunity to remove two central Allied leaders is just too good to pass up.
EDIT: Not Abwehr but the RSHA Amt VI, the SS foreign intelligence office
Three reconfigured type VIIF U-boats are sent, carrying Skorzeny's crack commando teams.
They reach the US coast undetected and slip into the wooded area. The conference is lightly guarded because no one believes the Axis capable of disrupting the meeting.
Just as Churchill and Roosevelt sit down for a chat, windows explode with machine gun fire.
The matter is kept secret from the public and quickly look-alikes are found to take roles of the top two Allied leaders.
EDIT: No doubles are possible.