How could the stars fight from their paths?
Rashi (from Tanchuma Bereishis 5): The head of the star was in Shamayim, and the other end was on the ground. 1
Radak: This is like "Shamah ha'Nechas Hashem Giborecha" (Yo'el 4:11; He brought down His mighty ones).
Radak citing Pesachim 118b: The stars made Sisera's army very hot. They were wearing armor; they entered Nachal Kishon to cool off, and it swept them to the sea. This is why the next verse discusses the river sweeping them.
Rashi: The length of a star is the thickness of the Raki'a. Since now the star reached from the Raki'a to the ground, this teaches that the thickness is the same the distance from the ground to the Raki'a (Tanchuma Bereishis 5).
