"So Joshua son of Nun called the priests and said to them, 'Take up the ark of the covenant of the Lord and have seven priests carry trumpets in front of it.' And he ordered the army, 'Advance! March around the city, with an armed guard going ahead of the ark of the Lord.'" NIV translation
Joshua relayed the instructions to the priests and to the army. He sent them out in the same manner as Moses had done (see Numbers 10) with part of the army in front of the priests with the ark and some behind them.
"When Joshua had spoken to the people, the seven priests carrying the seven trumpets before the Lord went forward, blowing their trumpets, and the ark of the Lord's covenant followed them. The armed guard marched ahead of the priests who blew the trumpets, and the rear guard followed the ark. All this time the trumpets were sounding." NIV translation
Why did they have to blow the trumpets? In Numbers 10, they were told to sound the trumpets when they were going into battle so that they would be remembered by God. This would have been like a royal procession and the people of Jericho must have wondered what was going on.
"But Joshua had commanded the army, 'Do not give a war cry, do not raise your voices, do not say a word until the day I tell you to shout. Then shout!' So he had the ark of the Lord carried around the city, circling it once. Then the army returned to camp and spent the night there." NIV translation
Imagine the sight as the entire army marched around the city without a word. The sound of the trumpets a constant reminder that the battle belonged to the Lord. They did as told and returned to camp for the night.
If we, as Christians, would remember this example and let the Lord handle our battles, then, more people might come to know Him. The Israelite army marched around the enemy in silence much as Jesus did when he was beaten, mocked, and even crucified. Too often, I find myself wanting to spring to the defense of Jesus instead of trusting in Him to defend me. When that happens, the problem is usually with my tongue as James warned (see James 3).