Trees were Cut Down by Besieging Armies for Erecting Forts
Source: TTT
Deuteronomy 20:20
But you may destroy the trees that you know do not produce fruit. Use them to build siege works against the city that is waging war against you, until it falls.
Jeremiah 6:6
For this is what the LORD of Hosts says: “Cut down the trees and raise a siege ramp against Jerusalem. This city must be punished; there is nothing but oppression in her midst.