LotR -- Book 5 - Chapter 04 - The Siege of Gondor

[Kuruharan]

Gandalf comes across as a little ‘callous’. He has his mission - the defeat of Sauron & the return of the King - to achieve, but it seems as if he has decided that Denethor is ‘surplus to requirements’. We see little kindness or compassion towards Denethor, or even an attempt to understand his position.

Denethor was unwilling to perform his function. His function was to step aside when the king returned.

(I would open the old can o' worms about exactly how legitimate Aragorn's claim actually was, but perhaps this is not the best place for it...)

See, Gandalf understood Denethor quite well. Denethor's impulse was selfish. He wanted the prestige and power of being the ruler. If the king comes back he can't have that anymore. This is hardly an attitude that we can expect Gandalf to sympathize with.

(This is perhaps a hard view of Denethor's job, and I seem to be wildly alternating from attacking Denethor to defending him and back again...)

I also think that you perhaps overstate the return of the king as being part of Gandalf's mission. While it would be nice, I don't think Gandalf (in a "mission from the Valar" sense) considered it vital. His job was to defeat Sauron. He was using Aragorn as much as he was using Denethor. Obviously things would turn out a little better (if you want to look at it that way) for Aragorn than Denethor under this arrangement. I guess it is true that Gandalf was not particularly concerned about that.