The Lord of the Rings: The Two Towers2002

[Camera slowly zooms in at the drainhole at Helm's Deep]

Gríma Wormtongue Helm's Deep has one weakness. It's outer wall is solid rock, but for a small culvert on its base, which is little more than a drain.

[Scene changes to Isengard, where Saruman is seen pouring gunpowder]

Gríma How? How can fire undo stone? What kind of device will bring down the wall?

[Saruman holds Gríma's hand back, which has a candle]

Saruman:
If the wall is breached, Helm's Deep will fall.

Gríma:
Even if it is breached, it would take a number beyond reckoning, thousands to storm the keep.

Saruman:
Tens of thousands.

Gríma:
But, my lord, there is no such force.

[Saruman walks Gríma outside as they are talking. At this point, Saruman reveals to Gríma the massive army]

Saruman:
A new power is rising! Its victory is at hand! [the Uruks cheer] This night, the land will be stained with the blood of Rohan! March to Helm's Deep! Leave none alive! To war! There will be no dawn...for Men!