Paratroopers!

[Denquin]

This idea is genius. In the Industrial Age (or the one after it) paratroopers could be unlocked at the factory. They could be deployed by air in enemy positions, where it is usually undeployable. However, this may require a few tweaks.

 

[Bigpapa97]

Interesting... Or maybe marines that come from the river? Or a boat that does a one time bombardment?