Complex sentence: In 1155, Pope Adrian IV, the only English pope, issued a papal bull (known as "Laudabiliter") that gave Henry II permission to invade Ireland as a means of strengthening the Papacy's control over the Irish Church.
Split into simpler sentences: In 1155, Pope Adrian IV, the sole English born Pope, issued a papal bull known as Laudabiliter. This gave Henry II permission to invade Ireland as a means of strengthening the Papacy's control over the Irish Church.