TEL AVIV — Israel dramatically expanded its aerial assaults on Lebanon with airstrikes Monday that killed nearly 500 people, wounded over 1,600 more, and appeared to signal the start of a broader military campaign.

Israeli officials said their forces struck 1,300 “terrorist targets” inside Lebanon that were linked to Hezbollah, the militant group that has been trading rocket fire with Israel for nearly a year.

It was not only the highest death toll this year on this front, it was the…