He took a yoke of oxen, and cut them in pieces, and sent them throughout all the borders of Israel by the hand of messengers, saying, Whoever doesn't come forth after Saul and after Samuel, so shall it be done to his oxen. The dread of Yahweh fell on the people, and they came out as one man.
Three hundred thirty thousand (330,000) men was indeed a near-miraculous response.  All of these events took place in only about a week's time, and during that period Saul selected an army, procured weapons for them, organized them and launched the campaign against Nahash.  Critics who wish to revise these numbers have nothing of any value whatever with which to replace them!