God was talking to Israel about the land he was about to give them.

(Deuteronomy 31:3-6 NIV) The LORD your God himself will cross over ahead of you. He will destroy these nations before you, and you will take possession of their land. Joshua also will cross over ahead of you, as the LORD said. {4} And the LORD will do to them what he did to Sihon and Og, the kings of the Amorites, whom he destroyed along with their land. {5} The LORD will deliver them to you, and you must do to them all that I have commanded you. {6} Be strong and courageous. Do not be afraid or terrified because of them, for the LORD your God goes with you; he will never leave you nor forsake you."

That has little to do with the idea that God is at work even when we don't see it.