Then all the Midianites and the Amalekites and the children of the east assembled themselves together; and they passed over, and encamped in the valley of Jezreel.
"And they passed over"  (Judges 6:33).  This is a reference to the hordes of the invasion crossing over the Jordan River.  Their encamping in the valley of Jezreel was due to the fertility of that region and the prospect of stealing all of the crops of the Israelites.  However, God had a great surprise in store for them!