Some time later Israel"s enemies from the East again crossed the Jordan and massed their forces in the Valley of Jezreel near Gideon"s home ( Judges 6:33). They numbered135 ,000 , or135 units, depending on the meaning of eleph here ( Judges 8:10). "Thousand" seems preferable (cf. Judges 7:12). This foray appears to have been the Midianites" annual invasion. [source][source][source]
Gideon wished to reconfirm the Lord"s promise to be with him and to lead him in victory against the enemy. Perhaps considerable time had elapsed between Gideon"s call ( Judges 6:11-32) and this new threat of attack. The Spirit of the Lord came upon (lit. clothed) Gideon in a special way strengthening and defending him for his great task ( Judges 6:34; cf. Genesis 28:20; Isaiah 59:17). He then sent out a call for men from several of the other tribes to join him and his family to fight the Midianites ( Judges 6:34-35). [source][source][source]
"When the "spirit of the LORD" first appears in Judges 3:10, it possesses Othniel, the first judge; and deliverance follows immediately. Here, however, when the spirit possesses Gideon, and despite the auspicious sign that several tribes fall into place when Gideon sounds the trumpet ( Judges 6:34-35), Gideon hesitates ( Judges 6:36-40). Apparently, the spirit is not effective apart from human participation ..." [1][source]