[The Squatter of Amon Rûdh]

The Men of Dale were fighting with Dain Ironfoot against Sauron's armies in the North. As Gandalf says:

When you think of the great Battle of the Pelennor, do not forget the battles in Dale and the valour of Durin's folk. Think of what might have been. Dragon-fire and savage swords in Eriador, night in Rivendell. There might be no Queen in Gondor. We might now hope to return from the victory here only to ruin and ash.

(The Lord of the Rings, Appendix A)

As for the Ents, it's a long way from Fangorn to Minas Tirith and they were mainly only interested in defeating Saruman, whom you'll recall they were left to guard. I don't think that they regarded the defence of Gondor as their concern.

[ August 10, 2002: Message edited by: Squatter of Amon Rudh ]