Malbim: It is Yisrael. Even though they believe in Hashgachah, they thought that Hashem saves through natural means, therefore they prepared swords and weapons. They thought that war pertains to man, just Hashem decides to make one side win. Now they will see that war is not via weapons. It is totally via Hashem; man need not do anything. Hashem will give your into our hands without bows, shields, swords or war at all!