I love the account of when Joshua set the 30,000 men behind the city of Ai to lie in ambush.  He set another 5,000 in ambush between Bethel and Ai. These men were to wait for a signal from Joshua. Until then they were to remain hidden and alert. 

The ambush was silently enacted. Joshua 8:20 says, “And when the men of Ai looked behind them, they saw, and behold, the smoke of the city ascended to heaven. So they had no power to flee this way or that way…”

I liken this strategic warfare as secret prayer. Revelation 8:4 says, “And the smoke of the incense, with the prayers of the saints, ascended before God from the angel’s hand.” There is more. Note the power.

Verse 5 says, “Then the angel took the censer, filled it with fire from the altar, and threw it to the earth. And there were noises, thunderings, lightnings, and an earthquake.” That is future. However, think of it as collective prayer from the body of Christ now. It is a call to ministry on our heart-knees.