[Maédhros]

It was my understanding that the Noldor had been utterly defeated and Morgoth had now an army so vast that Angband could no longer hold it. It was only the intervention of the Lords of the West and the armies of the Vanyar and the remaning Noldorin(and Men)army that managed to defeat Melkor.

Yes, but...
In Morgoth's Ring: Myths Transfromed:

If we consider the situation after the escape of Morgoth and the reestablishment of his abode in Middle-earth, we shall see that the heroic Noldor were the best possible weapon with which to keep Morgoth at bay, virtually besieged, and at any rate fully occupied, on the northern fringe of Middle-earth, without provoking him to a frenzy of nihilistic destruction. And in the meanwhile, Men, or the best elements in Mankind, shaking off his shadow, came into contact with a people who had actually seen and experienced the Blessed Realm.
In their association with the warring Eldar Men were raised to their fullest achievable stature, and by the two marriages the transference to them, or infusion into Mankind, of the noblest Elf-strain was accomplished, in readiness for the still distant, but inevitably approaching, days when the Elves would 'fade'.

The Ñoldor had a part to play in that too. And it was not only the Vanyar but the Host of Finarfin that fought in the war of Wrath.