Enemy Spawning System (ESS) by Enigx   Here my small contribution to Arma 3 community. Enemy Spawning System (ESS) is a simple and stable script for mission makers to spawn AI units on areas placed on map from editor. This ESS system is inspired to BangaBob's EOS system. I have used my spawning scripts for the core (created for other systems) to make a simple system especially useful for infantry spawning in single SP/MP missions. As a general configuration I used that of the excellent EOS system. Thanks to BangaBob!   Armaholic Enemy Spawning System (ESS)   Hey, it seems Armaholic has been shut down!! Alternatively, I added the file to this link which uses a personal external website (completely unrelated to the Arma game).
Features: Spawn infantry units, static turrets and vehicles A lot of preloaded units classname from different Mods Simple and stable particularly suitable for SP/MP missions Activation when players are close to the spawning area (ESS zone) Particularly useful for patrolling units and inside buildings AI units patrol the area without exit from it Saving of server resources Detailed guide step by step with addons SP and MP compatible   Installation / Usage: For instructions and information of how to use the ESS please refer to the included documentation and ESS_Call.sqf.   Notes:
Tested in many MP missions on dedicated without any problems. TIP: spawn of vehicles should be done in areas with no or limited presence of buildings and objects. A procedure is present in the script to select a "safe" spawning position for vehicles (taken from findSafePos.sqf of EOS), in order to avoid their placing on buildings, trees, walls... but that's Arma!! and it is not excluded that on some maps and conditions, spawining could interfer with objects on map with unpredictable consequences :-) 
Credits & Thanks:
Special thanks to BangaBob for sharing his EOS system. This ESS system is inspired by that.
Special thanks to Shuko for sharing his SHK_pos - Random position generator system.
Special thanks to Zenophon for sharing his Infantry Occupy House system. Thanks to Armaholic Community.
Changelog: Version 1.1 Added the possibility to have each light vehicle full of infantry units, specifying a chance value.   Version 1.0
First official version 1.0