Originally posted by knighttemplar1960:

Trolls can't walk over a moat, dry or wet. (Hint: they can't walk across a single core wood beam used as a bridge either) If you dig one far enough away from the tower, the log wielding trolls can't reach it. During the Viking age logs were used by groups of men as battering rams to breach stone walls and iron reinforced gates. It makes sense that a creature that is strong enough to wield a log as a weapon could use it as a battering ram to breach stone walls.

SO appropriate that you brought that up. In LotR during the siege of Minas Tirith, the Orcs brought up a huge metal headed battering ram. It was named Grond, after Morgoth's hammer that he wielded (rather unsuccessfully) during the second battle of the War of the Jewels. And "spells of ruin were laid upon it."
In the movie, Gandalf is rallying the guards as the gate is about to be breached. "You are soldiers of Gondor! Whatever comes through that gate, you will stand your ground!!"
Then the gate falls, and there are armored trolls with huge spiked maces. O_O
And then Sir Ian MacKellan, in a brilliant bit of acting, manages to say a crap-ton in just his facial expressions. "Me and my big mouth! WTF was I thinking?? Oh, well-no backing out now."