Convoked a council of ninety-three bishops, which excommunicated the iconoclasts, and the fleet which Leo sent to retaliate 273 on the Latin peninsula was lost in a storm in the Adriatic. The most Leo was able to do was to double the tribute of Calabria and Sicily, confiscate the pope's revenues there, and impose on the bishops of south Italy a servitude to Byzantium which lasted for centuries.
In 1030 he resolved to retaliate upon the incursions of the Moslems on the eastern frontier by leading a large army in person against Aleppo, but by allowing himself to be surprised on the march sustained a serious defeat at Azaz near Antioch.
Black Hawk, leading the party in opposition to Keokuk, at once refused to accede to this cession and threatened to retaliate if his lands were invaded.
In 1087 he invaded the French Vexin to retaliate on the garrison of Mantes for raids committed on his territory.