The issue is people are too full of pride they don't want to accept defeat IRL or in a game. They want to be the victor so they will just keep fighting no matter what, so they just keep fighting till someone gets bored and finally disbands their group. This happens time and time again and will continue to happen within DayZRP.
There should be a life system, if over the course of the war Group A loses 20 lives(player deaths) they would lose forces able to fight in said war. This would limit firefights as well as give an end goal of stopping wars before said group hits that number of lives lost. However, if you are at 5 lives left and make it 3 weeks before that number drops your lives would replenish back to full to put into affect that more people join your cause.