God was at the head of the army

Joshua 5:10-15
The day after the Passover, that very day, they ate some of the produce of the land:unleavened bread and roasted grain. The manna stopped the day after they ate this food from the land.
Joshua saw a man standing in front of him with a drawn sword in his hand. Joshua went up to him and asked, “Are you for us or for our enemies"? "Neither" he replied. "But as commander of the army of the Lord I have now come." Then Joshua fell face down to the ground in reverence.
“Take off your sandals, for the place where you are standing is holy.” And Joshua did so.
Why?
God was at the head of the army. No one knew this better than Joshua, after his encounter with 'the captain of the army of the Lord'. Israel knew it, as the Ark of Gods presence led the forces.
Joshua knew this man was send from the Lord so he fell down and listen to his command. His is the commander of the army of the Lord.
God's promis has done, after they ate the food from the land in Cannan, the manna stopped. Manna is the food to God's people provided from the Lord.
My food and my life is supported from the Lord either.
How?
God is my head rather me and anyone else in the world.