Plus it is in their best advantage to do small hit and run tactics like what the Americans did at the beginning of the revolution against the British.  For them to have "standing armies" trying to defend a border would be pure suicide.  They just have to hid, blend in and strike whenever they can.  Cheap tactic but it is the only tactic that they can use without getting slaughtered. 

I was pretty drunk last night so I didn't clarify "fair" chance too well. What I meant was that most of the major powers had a chance in winning. I am not counting Poland, Greece or any other small nation that wasn't really ready for the bloodshed that was about to happen. I was just considering Germany could have won the Battle of Britain, war against the Soviets, etc.. Probably the weakest "major" power in the war was Italy. They didn't really help out that much and usually got bogged down or provide weak protection on Germany's flank. I believe the Soviets crushed the Germans a few times by hitting the underpowered Italian forces trying to protect the flanks.

Also, not sure if I mentioned this before but I was wondering if anyone has ever played the Axis & Allies board game?  They made a few other variations of the it to (first one was the entire world map, then they made Japanese and German theater versions).  I just played the original (full world map).  I had a lot of fun with it and it has a lot more strategy than Risk.  The thing I hate the most about Risk is that one troop defending can kill off a decent size attacking force if the defender gets lucky and rolls 6s.  I remember one time I attacked with 5 or 6 troops in the beginning of a Risk game and he killed at least 4-5 of my troops.  The way it should be done is like what they do in Axis & Allies.  The attacker rolls first then the defender can choose whatever hits and put them in the casualty area.  Those troops can fire one more time before they are removed.  This is way more "realistic" and luck isn't as big of a factor.  I found it funny that it says on this site that the game takes about 180 minutes.  While some games can probably move that fast I've played games that spanned days with my friends while in high school and college.  I also like how each unit has a different attack and defend values to it (such as infantry only score a hit on attack if you roll a 1 but for defense it is 2 or less, tanks attack with 3 or less but only defend at 2 or less).

http://boardgamegeek.com/boardgame/98/axis-allies