Why does it say "l'Es Erev"?
Radak: This is when "va'Yetzei Mal'ach Hashem va'Yach b'Machaneh Ashur Me'ah u'Shemonim va'Chamishah Alef" (37:36)
Malbim: The verse depicts the terror that will come [on Machaneh Ashur] to confounding due to demons, which is at night.
What is "Valahah"?
Rashi: Demons will come against the enemy and confound it.
Malbim: Refer to 17:14:1:2.
What is the meaning of "b'Terem Boker Einenu"?
Rashi: [In the morning,] the enemy will not be in the world. Radak - "va'Yashkimu va'Boker v'Hine Kulam Pegarim Mesim" (37:36).
Malbim: The terror will be only in the middle of the night. In the morning, it will be clarified that it was nothing; it perished at night, as if it never was.
Who are "Shoseinu"?
Rashi: Sancheriv, and Gog and Magog, when they will come to plunder us.
Radak: It is Machaneh Ashur, which plundered Yisrael. The Navi says that this portion is proper for it.
Malbim: "Shoseinu" came to fight us; Bozezeinu are camps that came with them only to take spoils. Also they will get what is proper for them.