Did Denethor see Frodo captured in the Palantir?

[shadowfax]

Originally Posted by Alfirin

Especially after the Rohirrim arrive, since such a message might re-hearten Sauron's troops (however much Sauron may have relied on his troops fighting to the death out of fear of him, or because he could sort of puppet them (I'm thinking of the Trolls here.) there are presumably SOME officers among them (probably mostly men) whose battle tactics are a little more complex than "we have the numbers, meele randomly until we out swarm them. If your army is going to use trebuchets, battering rams and cavalry (not to mention barrusry) you sort of have to).

If I recall correctly, the realisation that the Corsairs were bearing reinforcements for the enemy did in fact dishearten Sauron's troops. So even if he considered them to be of little tactical value, they caused immense damage to morale. And even a relatively small amount of preparation might have seriously impeded the advance of the rangers, for example protecting the river banks with archers or even ambushing and delaying them further upstream or floating snags on the river. This might have taken but a relatively small detachment of the overall force being deployed on Pellenor at the time. It probably wouldn't have permanently stopped Argaorn's advance, but could have won valuable time and avoided the demoralising effect of Aragorn appearing on the main battlefield. Thus my own conclusion is that Sauron was unaware of who was on the ships.