Hezbollah

The Iraqi Shi'ite militias form a single, numerous and increasingly able component of the military and paramilitary assets available to Iran in its efforts. They substantially increase the scope for Iranian disruption in the region, and may significantly increase Iranian capabilities in the event of a war on Israel’s northern front

Lebanon has neither the desire nor the ability to address Hezbollah’s threat to its sovereignty. The likelihood of Lebanon suffering severe damage in a war against Israel does not change this situation.

The Folly of Supporting Lebanon’s Military.
Yossi Mansharof: Washington must acknowledge that the Lebanese Armed Forces and Hezbollah are allies.

The Shi'ite militia threat isn't a mere thought exercise about a worst-case scenario. Iranian-controlled Popular Mobilization Forces leaders have already threatened Israel only miles from Israeli homes.

Should a large operation inside Lebanon be considered after Hezbollah's tunnels are successfully neutralized?

Israel Moves to Seal Hezbollah Tunnels at Lebanon Border.
General Amidror: Now the ball is in the Hezbollah court. They can react – and the reaction to their reaction might be devastating.

IRAN'S LEBANESE CONTROL DEMANDS REEVALUATION OF WEST'S SUPPORT FOR BEIRUT.
General Amidror: Hezbollah’s bases will have to be destroyed by the Israeli air force, and there is no tactical way to do so without massive amounts of damage.

The Lebanese army should be treated as a hostile entity, its camouflage should be stripped away, and the American administration should be supplied with conclusive evidence of the multi-faceted cooperation between it and Hezbollah.

Hezbollah's Reign of Terror: From Beirut And Beyond. Comment by Prof. Efraim Inbar, The Jerusalem Post, 21.1.2018