Things You'll Need
Instructions
Build a setting for the game. Choose an aesthetic based on something like a historical setting or a fantasy one (created by you or inspired by existing fiction and fairy tales), this choice will help you determine the types of weapons, costumes (if any) and game mechanics and story (such as considering whether the game will contain fantasy and magic elements).
Make or buy weaponry to use depending on the type of combat contact you want in your game. If the contact is light, tag contact, you'll be able to use a wider variety of prop weapons, provided they don't have sharp edges. If you wish to create a battle game with full contact, explore options for safe foam weapons. (See Resources for help with homemade foam battle game weapons).
Build scenarios for your game based on whether you want the game to feature individual or team play. Team-play scenarios will involve two or more large groups battling for their team's domination, while individual play will have an "every man for himself" approach where a single person wins by completing the objective or fights off the rest of the players.
Offer an objective for the game. This could be as simple as trying to get the most "kills" to end the battle. Alternately, come up with a more complex objective, such as capturing something belonging to the opposing teams (such as a flag, king, or treasure).
List rules around the objective. Determine how different types of combat play will affect the course of the game in terms of what behaviors or contact cause a "kill" or "injury" in battle. If your objective is more than pure battle, come up with means of un-doing or limiting kill power to ensure that only achieving the objective wins.
Test play the game. Get together with a large group of friends and play the game, then accept feedback from the players about what should be changed to make the game more fun. Alter the rules and gameplay according to what criticisms seem to come up most consistently.