I think there's a link between plural marriage and wars. There always seems to be violence associated with polygamy.
Why do you think violence is linked with polygamy?
Men probably had to fight other men to take a new wife.
I think you have some misconceptions about polygamy. There is not any reported association between war and polygamy and a literature search would confirm that. People that are in plural marriages are not interested in fighting with others, they just want to live peacefully.