Israel's strikes on Iran's nuclear and military sites have pushed the long-simmering rivalry into open warfare, with Tehran retaliating and hitting key Israeli cities. With the US trying to balance diplomacy and deterrence,

Throughout the day on Friday, Israel carried out wave upon wave of strikes on nuclear facilities and missile bases in Iran. The Natanz uranium enrichment site and the nuclear facility in Isfahan have been hit and top military leaders have been assassinated - as have nuclear scientists.

Shapiro served as Deputy Assistant Secretary of Defense for the Middle East until January—charged with, among other things, considering scenarios in which tensions between Israel and Iran escalated into all-out war and preparing U.

Israel launched an expanded assault on Iran on Sunday, with direct strikes targeting its energy industry and Defense Ministry headquarters, while Tehran unleashed a fresh barrage of missiles blamed for the deaths of four people.

The United States is the main international backer of Israel, Iran's biggest regional foe. It is also a close ally of Sunni Gulf monarchies which for years pursued their own rivalry with the Islamic Republic, seeing it as their main regional threat.

In sweeping attacks that started early Friday, Israel has struck at the regime in Tehran, targeting Iranian nuclear and military assets. The Israeli strikes have killed more than 70 people, including four top security chiefs, and damaged Iran’s main nuclear site at Natanz.

The United States has pulled some diplomatic staff and military families out of the Middle East, citing unspecified regional security risks.

Iranian officials said on Friday that the United States "shall be held fully accountable" for its support of Israel after the nation took out key Iranian nuclear facilities and killed government leaders in a series of air strikes this week.