Battle Of Hydaspes
A great article in wondersandmarvels.com looks at a specific kind of combat engineering that was rare but incredibly effective. By having armies dig new streams and irrigation channels, life supporting water could be used to flush out enemies or dehydrate them by diverting sources. Lucius Metellus, a Roman fighting in Spain in 1423, dammed up a stream and then suddenly inundated a flood plain where his Spanish opponents were encamped. It literally flushed them away.
In 74 BC, Romans at war in Eastern Anatolia were fighting local tribes of people known as the Isaurians. The Isaurians fought well and when cornered, holed up in a town prepared just for this case. The Romans simply diverted the water source from the mountains and Publius Servilius noted that the Isaurians were “forced to surrender in consequence of thirst.”
Julius Caesar did the same in Carduci, a Gallic town at war with Rome. He diverted the various streams and thusly forced the Carducis to surrender.
The Exodus tale was a story of a battle, according the scholars. Moses led the Hebrews through what was then the Sea of Reeds, an effluvial swamp, which is to say that this swamp has a tide. Moses went through the sea when the tide was down and the Egyptians followed him with they heavy chariots into the soft muddy ground. This inhibited the chariots from sweeping across the desert to cut down the Hebrews. When the tide returned those who stayed with their entrapped animals and wheeled carts drowned.
Alexander faced opponents who used a river to divide the forces. In 326, in India at the Hydapses River, Greeks used the natural noise of the water to hide their movements as they crossed down stream and attacked the Indians suddenly from behind.
In Vicksburg, Grant used the Mississippi as a front to cut off and pin down the Confederates defending the last River redoubt against the Union. After six weeks of bombardment the Confederates surrendered and this effectively cut the Confederacy in half.
One of my favorite stories of rivers in warfare is the battle of Cowpens, when Banister Tarleton, the effete and cruel British commander was defeated by the middle aged Colonial Genera; Daniel Morgan. Morgan placed his forces in front of a river, one that gave them no where to run if they panicked. It worked, and the rest is history.
Geography can be a hard crucible against which defenders are tested.
Sources: wonders and marvels, ex temporaneous notes.