Valleys

You can't leave troops defending a valley because the food expense is too high. Then someone takes away your valley, but you don't find out until you look at the overview screen.

The solution is that after you take a valley you return your troops. After that reinforce the valley with one worker or one scout. You don't have to send a hero on a reinforce.

Then if someone attacks your valley it will show up on your reports and you can do something about it.

Remember, if someone else is controlling a valley, and they don't have troops there you can take it with a hero and one scout, now matter the level. (I haven't tried this, but it is what I understand.) Since scouts travel really fast, you can take the valley back pronto. Then deal with the larger issue.