Possible meanings are 1) the instruments of war refers to the soldiers who carry them and "hand" represents control. Alternate translation: "the soldiers that you command" or 2) the instruments of war are literal weapons and "your hand" represent both the king and his soldiers. Alternate translation: "the weapons that you and your soldiers carry" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-synecdoche]])
This term here is another name for the Babylonians.
# closing you in
"coming close to you"
# I will gather them
Possible meanings are 1) Yahweh will allow the Babylonians to enter the city or 2) Yahweh will cause the Israelites to bring their weapons back into the center of the city.