I read that someone posted Morgoths main weapon was fear and surprise attacks: this is sort of true. Most of the Battles that his armies fought used the overwhelming force tactic. Some of his battles were fought with the introduction of the new weapon, or th new weapon tactic (which someone has already mentioned). Two distinct examples of ths were when Glaurung first came out of angband (before he was fully grown and his armour was fully hardened), and in the war of wrath, wher hte host of the Valar destoryed almost all of his forces, and when defeat was iminent, then he used the New weapon Tactic by sending out the fire drakes, the greatest of which was Ancalagon the black.
Also, his main weapon, as has also been mentioned is fear and doubt. He instills fear by spreading lies and getting rid of peoples hope, and without hope (I quote from the story of Pandora's box in Greek mythology
there would be no point in living until tomorrow unless there is hope. He also instills doubt that his opposing armies can win. He sends a Massive army, and the sheer numbers of his armies overwhelm anybody mentally, even if they are the better fighters and would normally win. This does not usually happen, though, because all of the peoples have such a hate for Morgoth that they will do anything to stop his reign as Dark Lord. Ah, well. Just a few thoughts. Just wanted to sy thanks for al who have posted in this thread so far, and it will be a pleasure reading your replies in the future.