There is some selection bias as well - if they didn't invest heavily in military then the wars would not qualify as major barring other major imbalances highly

There is some selection bias as well - if they didn't invest heavily in military then the wars would not qualify as major barring other major imbalances highly unlikely to occur, such as "Conquistador Scenarios". If both were big and deterred no major war. If one was overwhelming then they either were the 800 pound gorilla sitting where it wants or the war was short by definition. Even if impactful it is the occupation which would gain focus of history. If both were limited in military strength they would find there was too much "friction" to do more than shift borders a bit even after handfuls died in skirmishes - they would be unable to hold big gains.