Age of Wealth and Peace

Era beginning/end

No war, only wealth.

Rapid population growth, technological upgrade (precision measurement), and big cultural event (horse tournament). This is the golden age of the kingdom, when the wealth comes to its peak.

However, the military just only changed a little bit. In fact, it didn't evolve for hundreds years as no war to be involved with thanks to an excellent diplomacy.

Nevertheless, it's fine after all. They're the wealthiest. What could happen?