One of the manifestations of God's strength for a People is their ability to arm themselves. This can be seen throughout the Scriptures all the way back in Genesis 14:14 when Abraham armed 318 men so they could reclaim his captive brother.
God does not always send blessings. Just as God fulfills his promises to bring good things on His People, when they leave Him and serve other gods, God also fulfills his promises to bring harmful things upon His People, up to and including total displacement from the Promised Land (Joshua 23:14-16).
When people turn to other gods, and those gods fail to deliver them, they end up oppressed. One of the first steps to oppressing people is disarming them. That's how the Philistines were able to oppress Israel: “Now there was no blacksmith to be found throughout all the land of Israel, for the Philistines said, ‘Lest the Hebrews make swords or spears’” (1 Samuel 13:19). Further, the Philistines heavily regulated anything the people of Israel could do by which they could circumvent the ban on anything that could be used as military-style assault weapons (1 Samuel 13:20-21).