Rashi: Due to the scare of one enemy, 1000 of you will flee "and due to the scare of five, [all of] you will flee."

Rashi: This is like Asher Nosartem. Radak - we find Im in place of Asher, e.g. "Ad Im Dibarti Davarai" (Bereishis 24:33). It can be in place of Ka'asher, e.g. "v'Im Yihyeh ha'Yovel" (Bamidbar 36:4). You will flee so much that those who remain will be few among many, like a mast on a mountain top; from afar, it looks like it is the only one.

Rashi: It is a tall wooden beam inserted in the ground, like the mast of a ship.

Rashi: Also this is a tall beam. They put it on a hill top, and when the lookout sees troops coming, he puts a scarf on it, and the wind blows it, and it is a sign that they should flee or gather.

Malbim: It is the curtain (sail) that they put on the mast. The Toren represents isolation, just like a mast is a lone beam on a ship; everywhere, the Nes represents gathering for war. If you will flee to the high mountain tops, where mountain goats are, you will be alone like a mast. If you will descend to the nearby hill, which is lower, you will be like a Nes to gather nations for war, and you will need to resemble a deer (flee quickly).