What sword is discussed?
Rashi: Troops for war.
Why does it say "Al ha'Aretz"?
Radak, citing Sifra: This is the only place where Al ha'Aretz means El ha'Aretz.
Why does it say "v'Amarti Cherev Ta'avor ba'Aretz"?
Radak: It does not say so regarding Chayah or plague, for it does not mean that I told them via my Nevi'im to warn them. No Navi was sent to Sedom and Amorah! Sechel warns about Aveiros like these, that intellect teaches them. Rather, before the sword comes, people tell before it comes. Travelers say 'Melech Ploni is coming to this land.' It is as if Hashem said so. Similarly, it says "v'Hichrati" ? the army that comes cuts them off, but Hashem aroused their Ru'ach to come against them. However, when Chayah or a plague is sent to a land, no one tells before it comes.
