Various world leaders and institutions have raised their concerns that the presumed Israeli strike in a suburb of Beirut, Lebanon, that killed a top Hamas leader could escalate and expand the conflicts in the region. Deputy leader Saleh al Arouri — who was allegedly responsible for leading multiple attacks on Israel and had ushered in a closer relationship between Hamas and Hezbollah, the Iranian-backed militia in Lebanon — was one of a handful of people killed in the Tuesday night strike. His killing marked a possibly pivotal moment in the powder keg that is the Middle East. Israeli leaders have...