I started an expedition yesterday, fought a couple of camps to get an idea of the mechanics then cancelled the expedition. Today I started a new expedition and the lost troops from the previous expedition counted towards my troop limit for the new one. Also I send some troops home with an Expedition supplier and those troops were also counted towards the troops lost.
Also when you are at an expedition and you click the show details button (from the quest popout), you get the statistics for the expedition. There are two buttons on this window - a return home button at the bottom and a close (x) button at the top right. Clicking the close button also sends you home. Surely it should just close the window?