On the main page is given a description of warfare in planespace.
However, I would like to point out that this is quite possibly the least effective military formation, and a hideously silly way to conduct a war.
One boat is needed for all your men to cross a body of water. This boat has a rope attached to the rearward end of it. The other end of the rope is anchored to land. Once the boat is across, the rope is removed and then anchored into the ground on the other shore, and all the men can cross. Even a rope makes an excellent bridge, since the rope cannot sink beneath the water, and the men cannot fall off. When done, the rope can be cut or rolled back up. In fact, you may not even need a boat! A harpoon gun would work wonders!
Marching one-on-one into combat is only needed in a linespace war. The second dimension has been completely ignored! Indeed, now that the enemy has far less chance to dodge than in realmspace, the archer reigns supreme. You send a few soldiers forwards to claim ground, while the rest of your forces hastily raise a towering flagpole with platforms hanging off one side, and a pair of ropes hanging off it into each direction. The rear-facing rope is pulled taut and hammered into the ground to form a ramp to the top. From the top, they use the other rope to climb down into alcoves that face the front lines. Once the alcoves are manned, the rope must be pulled up out of the way so as not to obstruct vision. Each man has a bow and a shield. When raised, the shield will completely defend from all incoming fire, but the shield must be laid on the floor of the alcove in order to use the bow.
Another major oversight is jumping! One would have to assume that if you cannot pass around neighboring creatures, the ability to jump several times your own height would be a prerequisite for survival. When the wolf comes for the sheep, it is not effective to have the sheep simply run until it hits an obstruction and then die. No, in war your planespace men would be bounding around like mexican jumping beans, pouncing upon enemy lines and stabbing downwards vigorously.
Guided missiles can also be seriously considered due to the ease in hitting the target. Airplanes are much easier to design, the entire plane being a cross-section of a wing with an engine on back.
Please feel free to expand on this topic with tactics for wars in higher or lower dimensions. Though a war in linespace is -really- boring, and perhaps impossible if linemass cannot be created or destroyed.