See Map key (Imp2).
Province with unit but no fort - Imperialism IEdit
Joe Krishna Mithiran reported on Imp list:
"If you have at least 1 unit in a province without a fort and are attacked and don't place any of your units on the map, you will automatically win. If you have a fort and do this you will crash the game."
Detailed method: "The computer asks you if you want it to deploy your troops for you. Click cancel. The map of the battleground comes up - click on the end deployment button on the right of the screen (the two crossed swords). The computer places its troops then asks you again if you want it to deploy your troops for you. Again you click cancel and then when the map of the battlefield comes up you click on the 'end deployment' button with the 2 crossed swords. You win the battle"