[Fate]

The jeff is right about sneakers. If they attack the province they are IN (not an adjacent province) one of two things will happen:

1) A friendly magic attack happens that turn. The sneakers join the magic battle.

2) No magic attacks. The sneakers attack during normal battle phase (with other allied forces if there are any).

3) There is a non-friendly (neutral or enemy) magic attack. This situation is a bit sketchy (search for ghost riders+scouts for the full details), but it appears the sneaking attackers will join in the magic battle phase and attack with their own battle (before or after the magic armies). This is not generally a worry unless one or both sides are casting lots of remote attack spells (especially the summon neutral attack ones).

A final point, defending sneakers are not affected by any of this. They are always either defending/patrolling (and then are treated just like any other defender) or hiding (and then they do not fight at all).