In military history, a nutcracker is where two nations, either side of a strong one attack on both fronts, making it near impossible for the cracker'd country to win. This was how world war II was won, when the soviet union attacked Germany, eventually pushing it inwards. The best defence against this is to merely use a small battalion of guerilla-styled troops to bombard all the attack points of the weaker and less enthusiastic enemy with long range weaponry, while taking the main army to the main enemy. The weaker enemy will just camp up while the stronger enemy, disheartened to hear the nutcracker did not work, will have to go solo.
The French attempted to nutcracker the English and Welsh by means of alliance with Scotland. When the countries united in 1705, the new United Kingdom was an almost invincible force on home territory.