In the midst of thy camp; either because the ark was commonly present with them, or at least some of the holy instruments, which were pledges of God's presence; or because God had promised to go forth with them when they engaged in a just and necessary war.
Related Commentaries of Deuteronomy 23:14
Deuteronomy 23:14
14 For the LORD thy God walketh in the midst of thy camp, to deliver thee, and to give up thine enemies before thee; therefore shall thy camp be holy: that he see no uncleanb thing in thee, and turn away from thee.