Of Manasseh also there fell away some to David, when he came with the Philistines against Saul to battle: but they didn't help them; for the lords of the Philistines sent him away after consultation, saying, He will fall away to his master Saul to the jeopardy of our heads.
"Until there was a great host, like the host of God"  (1 Chronicles 12:22). This is a reference to the ultimate rally of all Israel to the kingship of David and should not be understood as applicable to the period of David's long contest against Saul.