During the 2006 war, Israel attacked Hizbollah positions with air power and artillery during the first week. As the second week began, Israel advanced into Lebanon with armor and infantry. When they encountered the fortified Hizbollah troops, the IDF bogged down and began taking a couple dozen casualties. When Hizbollah began destroying the Merkave tanks with shoulder launched weapons, the IDF withdrew back across the border and never crossed again except for a couple of special forces missions. The IDF had about 120 killed during this war and they had enough. Any thought of rooting out Hizbollah and dealing with Nasrallah was abandonded as too costly. The last thing that Israel would do is to invite Iran to make a massive missile barrage on Israeli targets. It would be out of control. Nobody knows how bad it would be. Inviting this risk is not something Israel would do.
from the article: Germany: Israeli military strike on Iran unlikely to succeed