Israel has long experience in playing off Palestinian divisions and deepening them , whether it was trying to favor one or another of the groups in the original Palestine Liberation Organization , or encouraging Hamas in the 1980 's as a seemingly benign Islamic alternative to Yasir Arafat , or trying to deal only with Palestinian mayors and clan leaders in the West Bank and Gaza before Mr. Arafat and his lieutenants returned from exile in 1994 after the Oslo peace accords .