Radak: There will be blood in the land from the great killing, and fire and smoke in Shamayim - lightning that burns when it descends, and the fire raises smoke. This is a sign for the plague that will strike those who come with Gog and Magog against Yerushalayim.

Malbim: After saying that Da'as Hashem will be revealed in the land via Nevu'ah and Ru'ach ha'Kodesh, it says that they will recognize Him also via supernatural wonders. (a) The Resha'im will be punished via "Dam va'Esh v'Simros Ashan." Dam is in the land - the sword that will be in the army of Gog and Magog, like I explained in Sefer Yechezkel. In Shamayim will be fire - Hashem will rain on them Esh v'Gafris and Avnei Elgavish, and there will be smoke from the great burning. (b) Refer to 3:5:1:2.

Rashi: It is smoke that goes straight up (Radak - pillars. They are called Timros, because a Tamar (date tree) is tall and straight. Chazal said about smoke 'from when Timraso rises' (Brachos 43a). Beis Avtinas knew to make Ketores so that the smoke will be Mesamer v'Oleh (go straight up); others were able to compose Ketores, but the smoke spread here and there (to the sides; Yuma 38a).)