Board Thread:General Discussion/@comment-4010415-20141223120240/@comment-24994749-20150611001734

Oobleck did say the turning point was 3 years into the war, but we don't know for how long it dragged after that... or if it dragged for a longer period of time in certain Kingdoms than others.

There is also the possibility that full blown war only blew up after a long period of time of escalating smaller conflicts. So, even if the war itself was resolved in less than a decade, you would have to add the damage of the previous years.