[JeffF.]

The overall populations around Northwest Middle Earth seemed small (as the author of the Atlas of Middle Earth points out). Every Dwarf hold mentioned except for the Iron Hills is described with words as 'small' or 'few.' The account of the last battle of the War of Dwarves and Orcs shows that the Dwarves suffered immense casualties. Thorin's description of Smaug's decimation of Erebor states that only a few dwarves who were outside the mountain escaped and most were killed. Earlier the Dwarves of the Ered Mithrin had also all been killed or driven away by the dragons who coveted their wealth. These accumulated disasters must have had a drastic effect on the numbers of Durin's Folk. I'd say my estimates are only possible if dwarves of other houses joined the recreated Kingdom Under the Mountain. "Grown strong again" has to be put in the context of these previous losses.

Gandalf's knowledge of the composition of the enemy armies I take to be a result of his mind battle with Sauron (as he describes upon his reunion with Aragorn/Legolas/Gimli. Much like Frodo's vision of the Easterlings as he wore the ring to escape Boromir. Gandalf's description that the Enemy has few horsemen is not based on any immediate reports (the besieging army has only begun to cross at Osgiliath).

I notice that the Atlas of Middle Earth shows only Rohan as being composed of 'plains' and that for most of the clear areas depicted in the maps of LotR she describes as partial woodlands (compared to pure woodlands like Greenwood and Lothlorien). No doubt plains must have existed in the East, the Wainriders (who mainly used the chariot) must have evolved in such a land but for me the bottom line is Gandalf's description. The books should be regarded as canon except when there are contradictory statements and later statements made that correct earlier thoughts or descriptions.