Everyone knows the Second World War was won on the playing fields of Hogwarts.
(Call of Potter: Wand at War?)
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Then we have the female SOE ninja assassin:-
Presumably she can get in to hand to hand fights with the Nazi fetish girl on top of a Zeppelin or something.
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And don't forget the (whatever) Firefly.
Take an American mech (or golem, or giant monster, or whatever) and
strap the biggest gun you can find to it.
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And if we are talking Great War, there is the Contemptible. Britains pre war army (which became known as the Old Contemptible) was very small by European standards, but well trained. Naturally, trained soldiers were far to valuable to sit idle just on account of having been killed. So many were brought back to life by the technologies of Herbert West (reanimator) and put back in to the line. Over the course of the war, additional improvements were made to them, and by the Berlin offensives of 1920, an average Contemptible stands ten feet from the bottom of their hooves to the end of their horns, can wield a specially modified pom-pom in each hand, and is quite, quite mad from all the excitement.
And after spending the inter-war years in storage, the program could be reactivated to fight the Nazi scourge.
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And there are the SAS and the Commandos. And British Paras were known as the Red Devils, which obviously means that a dark ritual has turned the entire unit in to Hellboys.
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And Churchill. As we all know, Churchill was lethal with a submachine gun.
This picture was taken shortly before he led the final assault on the Reichstag in an attempt to prevent Hitler fleeing by rocket to the Nazi moonbase.
http://www.grippingbeast.com/product.php?ItemID=2578(As we all know, Churchill actually killed Hitler (the first time) with the Mauser C96 he carried at the Battle of Omdurman, loaded with silver bullets blessed by the Archbishop of Canterbury to overcome Adolfs occult defences)