To get a real war going you want some advantage to escalation. Simply spitting it in proportion to the total giving diminishes the value of a marginal dollar. Maybe an all-pay auction (like a dollar auction) would be better: whichever of AMF and CFAR got more donations would get the full match from me. Among rational mixed-strategy-utilizing donors this should result in $X moved by an $X pool on average, but people being imperfect I would expect to see more than $X moved.