David takes an extra precaution with regard to Saul. Though Saul said he would no longer search for David, David had heard that before. Thus, he goes into the land of the Philistines. While there for the 16 months he was a treacherous player against the Philistines, and they were none the wiser for it.
Application: This is a difficult chapter for me; it’s not difficult to understand, but it is difficult to understand why David did what he did. I know the common replies, but they seem inadequate to me; David actually deceived the Philistines and destroyed the innocent and warrior alike. Though I may have my struggles in understanding some particulars about this, I know that He who knows all knows all!