Another way to describe war is the effect it has. A horrific war. A tragic war. (big impact, many casualites implied) Political unrest. Military confict. (small impact, not as many causalites involved).

Usually we talk more about the casualties involved and time, rather than the size. We talk about a long, bloody war. We can also talk about a short, relatively bloodless war (there don't seem to be many of those). If a number of countries are involved, we would talk about a war that drew in X nations, rather than just saying huge.