1)
What is the meaning of "ha'Lanetzach Tochal Cherev"?
1.
Radak: Will your sword consume (kill) flesh forever? I know that your lust for war will be bitter at the end.
2.
Malbim: The purpose of the fighting was to see who will be Menatze'ach (defeat the other, i.e. who is stronger), not that the sword will consume (kill) flesh!
2)
Why does it say "Marah Sihyeh ba'Acharonah"?
1.
Ralbag: No matter who wins, it will be bitter in the end!
2.
Malbim: When there is a purpose to the war, even though spilling blood is bitter, there is a sweet end (the purpose of the war). To kill without purpose is bitter [also] at the end.
