Thirty-four years ago today, Iran began its blood feud with America.

On Oct. 23, 1983, a suicide bomber drove his explosives-laden truck into the U.S. Marine barracks in Beirut, Lebanon. His bomb killed 241 U.S. service personnel, mostly Marines.

While Iran has long sought to hide its responsibility for this act of mass murder, the evidence indicates the attack was carried out by an element of the Lebanese Hezbollah and under the orders of the Iranian government.

Aside from the moral impact of fallen Americans, Iran's involvement here gives all Americans a strategic interest in reminding themselves what happened that day. Because Oct. 23, 1983 laid the foundation of America's enduring relationship with Iran.

Consider that by 1983, U.S. hostages held in Tehran had been home for over two years. Moreover, the U.S. military mission to Lebanon was designed to support that nation's beleaguered government and counter growing violence from various Lebanese sectarian blocs. The Marine mission was neither designed nor effected to target Iranian interests. Instead, as the Beirut barracks memorial attests, the U.S. Marines "came in peace."

Iran, however, came to Beirut with a very different mission. They regarded American influence in Lebanon as incompatible with their theological mission to dominate the region under Khomeinist-hegemony.

Nothing has changed since then. After all, since 1983, Iran has pursued dozens of terrorist plots against America, pursued an industrial-level kill-and-maim campaign against Americans in Iraq and Afghanistan, and sought to destroy U.S. allies from Baghdad to Beirut. Ultimately, Iran carried out these attacks for the same reason that it carried out the 1983 barracks bombing: because they know that in order to dominate the Middle East, they must first push the United States out.

Don't get me wrong, my contention here is not that we should meet Iran's malevolence with war. Yet we must recognize the sustaining theme of Iranian policy towards America between Oct. 23, 1983 to Oct. 23, 2017. That clear-eyed appreciation for reality is crucial as we seek to improve the Iran deal. Crucial, because diplomacy with Iran is possible, but only if sourced in realism rather than idealism.

Put simply, the Marine barracks memorial and 34 years of history remind us to deal with Iran as it is, not as we would wish it to be.