Cost.
Of course, it could also be considered as profit.
Looking back, especially after the first Global War, whether it's global warfare or local conflicts, the investments in almost every war far exceeded the returns. Therefore, even if the war was won, it was still a loss, turning warfare into a losing business.
This often led to wars being used as tools by politicians to realize their personal ambitions.
Some might think this is good for maintaining peace.
Clearly, such an understanding is very superficial.
War is never the ultimate goal, just a means to achieve an end.
Furthermore, both war and its counterpart, peace, are actually relative.
There is no absolute war or absolute peace in this world. Both are merely relative forms in the international community and national relations.
To put it directly, there is essentially no permanent peace.
