Joshua 6:1-27 says Joshua commanded the Jewish people to circle Jericho for seven days and to "not shout nor let your voice be heard, neither shall any word proceed out of your mouth, until the day I bid you shout; then you shall shout." Josh. 6:10. Was keeping a million men, women, and children silent a miracle, or was it evidence that that generation was just incredibly disciplined? Did Joshua command them to do this because G-d wanted it, or did he have other reasons? What might those reasons be?
Ralbag explains that the reason for the silence was so the inhabitants not hear them. Thus, presumably, they could speak quietly, and the "וְלֹא יֵצֵא מִפִּיכֶם דָּבָר" was overly emphatic in order to make sure they didn't speak loudly. (Note that that command to be quiet was not noted as having been fulfilled, and I have no reason to think that the entire crowd was perfectly silent. Note also (verse 3) that the only people right near the city were the soldiers and kohanim.)
Well, keep in mind that because the Israelites couldn't keep their mouths shut (always complaining) the whole nation had to wander in the desert for 40 years until that older generation died off. Joshua has a chance now to take possession of the Promised Land and he didn't want anyone to ruin it by speaking unbelief or complaining about their strategy.