Passage: Trade between the Muslim eastern and southern shores and the Christian northern shores almost ceased during this period, isolating Western Europe from developments in the Muslim world: "In antiquity, and again in the high Middle Ages, the voyage from Italy to Alexandria was commonplace; in early Islamic times the two countries were so remote that even the most basic information was unknown" (Kennedy). Muawiyah also initiated the first large-scale raids into Anatolia from 641 on. These expeditions, aiming both at plunder and at weakening and keeping the Byzantines at bay, as well as the corresponding retaliatory Byzantine raids, eventually became established as a fixture of Byzantine–Arab warfare for the next three centuries.

Question: what were these expeditions aimed at?
weakening and keeping the Byzantines at bay