The union of Maedhros was a alliance, not an army. If it was about the best allied armies then the hosts of Tar Minastir's fleet with Gil Galad's diminished force are the best bar the undead/Valar, which singlehandedly slaughtered Sauron's forces, which were already on the way to conquering middle earth.

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"This is the hour of the Shire-folk, when they arise from their quiet fields to shake the towers and counsels of the Great. Who of all the Wise could have foreseen it? Or, if they are wise, why should they expect to know it, until the hour has struck? "