Ego battles should be played by hand/wrestling/boxing/any other way(not said funnily) by the heads of the state if they are real leaders, rather than sending highly capable troops to kill troops and innocent citizens of the other nation state.
Anyway, people would be left with only this option After (if ever) World War 3 happens.
An eye for an eye, blood for blood, etc. is the retributive method used only by the weak leaders who do not even care about their own people.