This verse apparently refers to the practice among the pagan Babylonians of worshiping and offering sacrifices to their weapons of war. The Babylonians were on a mission of world conquest in Habakkuk’s time. Bowing down to these weapons was the Babylonians’ way of strengthening and dedicating themselves for this purpose.
This pagan practice made it difficult for Habakkuk to accept the reality that God would use the Babylonians as an instrument of judgment against His own people, the nation of Judah.
HABAKKUK 1:16 – They [Babylonian warriors] sacrifice unto their net, and burn incense unto their drag [dragnet, NIV].