The Islamic state captured Arsal, Lebanon, following fighting over the weekend. Reuters

The Islamic militant group formerly known as ISIS on Monday captured the town of Arsal, Lebanon, following a three-day battle with Lebanese military forces, in a move that underscores its decision to drop "Syria" and "Iraq" from its name (formerly Islamic State of Syria and Iraq, now Islamic State).

The battle caused the death of 13 Lebanese soldiers and at least 50 Lebanese civilians; fighters for Islamic State (IS), formerly Islamic State of Syria and Iraq, also took some Lebanese government officials hostage.

According to the Telegraph, the IS offensive was triggered by the Lebanese arrest of Abu Ahmed Joumaa, the leader of a small brigade of the Free Syrian Army that had declared itself loyal to IS. Hezbollah, the Iranian-funded Shia militia that has long operated in Lebanon, has vowed to help the Lebanese army recapture Arsal. Although the city lies on the Lebanese side of the border, the vast majority of the present population consists of Syrian refugees.

Since its capture of Mosul, Iraq's second-largest city, in May, IS -- then ISIS -- has gained control of a wide swath of Iraqi and Syrian territory. The organization subscribes to a radical form of Sunni Islam and was once expelled from al Qaeda due to concerns that its brutality would alienate local populations.