What was the mission behind the Marines shelling of the Chouf mountains in Lebanon in 1983?

What is so special about the region?
Other than that there is a Druze population there & Sh’a.

They say that hashish is mainly grown within Biqaa Valley.
Why were the Americans choose to use the USS New Jersey against the civilians in this area?

The Marines were asked to come in by the Lebanese government. The Israelis had invaded Lebanon and we sent peace keeping forces. Reagan sent in 800 Marines but was required to withdraw them within 30 days according to the War Powers Act. After the withdrawal 1500 Marines were sent in 2 weeks later.

Reagan said it was essential that Israeli forces withdraw. The Israelis continually harassed the Marines. The Israelis were going to withdraw and we asked them to delay the withdrawal so we could get Lebanese troops in position. The Israelis withdrew, leaving the Marines in a crossfire between Syrians and the Lebanese. The Syrians (muslims) were attacking the Marines and we were firing back.

Lack of resolve from the Reagan administration ended in the deaths of many marines.