Question:
In Genesis 26, Isaac (who was clearly stronger) made a pact with the Philistines. Now, as we know, the Philistines killed many Israelites until David’s time. Was Isaac responsible for the many deaths and difficulties of the Israelites? He could have easily killed all of the Philistines. He didn’t appear to ask the Lord’s guidance in that matter either.

Answer:
In Genesis 26:3, 4 the Lord confirms with Isaac the promise He made to his father Abraham. He was called to “sojourn” in the land, meaning he was to live in it but would not own it as his own property. Hebrews 11:13 says these men of faith were “strangers and pilgrims” who by faith were sure of the possession of their inheritance, but at a future time. So Isaac was not called by the Lord to take the land by warfare against the Philistines.

It was when God made a covenant with Israel that He called upon them to destroy all the nations that occupied the land of Canaan. See Exodus 34:10-13 and on. See also Deuteronomy 7:1-8. The Philistines were not originally one of the Canaanite nations but were a very warlike people who took possession of a coastal area in the south of the land, and were already very strong at the time of the Exodus. Because of their possession of this part of the land that God gave to Israel, they too were marked out for destruction by Israel.
We can see then that Isaac had no responsibility for the future woes of Israel because of the Philistines. The nation itself bore this responsibility because they failed to obey the Lord according to His covenant, thus becoming powerless to deal with their enemies. Also, we can fairly say, as we understand Isaac’s place in the land of Canaan that it was right for him to learn to live peaceably with them.