Excluding some unusually bloody wars (like the Thirty Years' War), most war was perhaps a bit more small scale than one might think. They might have been on the order of hundreds or thousands of soldiers instead of hundreds of thousands. Demographic signatures of major wars do show up, but for most men and women throughout modern history, the main causes of death were disease, both infectious and chronic.

With that said, there definitely are demographic signatures of some wars. The USSR, for example, is still recovering from its 17-20M citizens lost in WWII, and some Scottish towns suffered a near 50% casualty rate in WWI.

I hope this helped a little bit, and I hope others can provide more insight.