No, War is not inevitable. But we must address multiple means for stopping it. And these are many. Just one is to analyze our language. The 'War on Cancer', for example, implies that war has a good outcome and if you die of cancer, you lost the battle. The practice of competition which we encounter from our earliest schooldays easily slide into 'battle/war' language-and into 'battle/war' behavior.
Years ago when I was designing a peace education program, I met a diplomat from Botswana who said that his country has a comprehensive peace education program that works. More recently, I asked another Botswanian if the program was still effective. She said yes but was being put under strain by the discovery of diamonds.
Costa Rica, which had abolished its army, and Botswana remained at peace while their neighbors in Central America and Africa fought to exhaustion and economic destitution.