Age of Empires II: Definitive Edition (PC) - Achievement - Unchivalrous Pragmatist
Defeat Simon the Younger's army before the baronial forces attack in "Vain Ambition".
This achievement is fairly straightforward. Once you escape in the beginning of the mission, make your way to Worcester (Grey) which will be visible on the map. Once there, you will take control of the camp. A timer will begin signifying the time you have until the enemy realises you have escaped. This is NOT the timer you need to adhere to. Once this timer ends, ANOTHER timer will begin signifying the time you have until the enemy attacks. You must defeat Simon the Younger's army before THIS new timer expires to obtain the achievement.
Simon the Younger is camped not for East from your town of Worcester. You should have plenty of time to raise an army strong enough to defeat him and his troops.
Note that whilst his army colour is blue, you do not need to defeat all blue forces, just the ones around Simon the Younger to the road East of your town.