Same as '44 is the first "Final Solution to the Hitler Question" which comes to mind...
Various opposition groups had been trying to blow up the Mad Housepainter since '38 or '40, but everything from failing fuses to fizzled plots kept saving the Bohemian Corporal's butt...
Heck, if somebody would have had the nerve (and most likely a death wish) they could have simply walked up to him and shot him in the forehead...

The ending of the war is the tricky bit.

Presuming a resoundingly successful assassination attempt, like, let's say, blasting the Berchtesgarten(sp?) off the face of the earth with all the major nazi bigwigs at some sort of mutual ego-stroking conference within its walls, this would free up the heads of the military to form some sort of "special executive commitee", or whatever, and take over.
Presuming its 1943, there may be a slim chance of ending the war on a positive note for Germany, but the first thing which must be done is displaying your killed off nazis and making up some story about how the war was all their doing and we'd be happy to call it all off and make amends now that the bad, evil National Socialists are all kaput...
The Western allies might actually fall for this, especially America, since it would free up resources to hurl against the Japanese... Probably not, given FDR's "Germany First" policy, but if the shooting really stopped, who knows?
Your real problem is Crazy Ivan, who is now EXTREMELY pissed off, on the offensive, digging up mass graves and discovering razed towns & such...
With loads of good fortune, and a VERY convincing "awww, gee whiz , we're really sorry, but these crazy bolsheviks just won't play nice & negotiate" routine, you might be able to get the West to put pressure on the Russians to cut a deal for all of their territory back and some miscellaneous amount of cash reparations to be settled later...
You know damn well Crazy Ivan is coming over the wall again no matter what the deal and treaties that are signed, but at least this gives you the breathing room to retool, and stop the Anglo-American bombing campaign...
Maybe the mythic Western alliance against the Russians could even be trotted out once the Russians decide they want to conquer Europe after all!



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Novus Ordo Seclorum