This is an important place because you will store your Weaponry and Ammunition here. Make sure it is well defended, because if the enemy team gets to it, they will have a bounty of items to use.  One idea is, to have a reliable easy security system. During a Nerf War, have at least one person who guards the fort. Another good plan is to have other little bases in the area, so if you main base is captured by the enemy, you can retreat to a smaller base to regroup your team and nerf guns This will be the main station for organizing campaigns, creating alliances, etc. If this falls to the enemy, you must have a secondary capitol, as well! Start with large cardboard boxes for indoors, and wood for outdoors! Also, cover cardboard with duct-tape to make it somewhat waterproof! Add a flag with a voted on sign, and a couple of windows with covers for rain and for ambushes! Add 2-4 cardboard boxes for turrets, with flags and holes for shooting. You may want to also add little turrets (outposts.) in areas to secure, either keeping them empty and camouflaged for emergency use, or stationing units in them! Most outposts should be small, inexpensive, and pretty easy for the enemy to overcome. They are mostly used as warnings, and as emergency posts for the wounded/for cover. It's important to have supplies on hand in just about every station (including outposts.), because in the event of a siege, you can hold out for a longer period of time, with ammo, food, drinks, etc. Having communication devices are handy, as well, so you can call for back-up, or supplies, instantly.

Summary:
Construct a base. Build a Nerf capitol! Build “colonies”, of little bases to show territory, along with secondary and tertiary capitols! Make all capitols and bases with supplies and a map pinned-up, so you can mark territory, mark where bases and units are staged, and present a battle-plan.