Israel targeted nuclear and military sites in Iran in airstrikes early Friday morning.The strikes are a major escalation that threatens to expand into a wider regional conflict.These are five key questions in the wake of Israel's air war.

An aggressive counterattack risks escalation. But giving in to U.S. and Israeli demands is an unlikely alternative.

Iran began its retaliation campaign early Friday, after warning Israel it would pay a “heavy price” for its attack.

In response to Israel’s attack, Iran fired back with more than 100 drones. NBC News’ Chief International Correspondent Keir Simmons reports more. Former NATO Supreme Allied Commander retired Gen. Wesley Clark and Senior Fellow at the Carnegie Endowment for International Peace Aaron David Miller join Ana Cabrera to examine the possibility of further attacks.

Senate Minority Leader Chuck Schumer is the only one of the top four congressional leaders not to react so far

Sirens sounded in Israel as the Israel's military said Iran launched ballistic missiles and more than 100 drones in what appeared to be the start of Iranian retaliation for Israeli strikes on its nuclear facilities.