Transcript for Mourners in Iran vow revenge for Soleimani’s death
These young American servicemen and women are the first wave of military troops arriving in the Middle East amid the growing crisis with Iran. 3,500 strong joining the already tens of thousands of U.S. Troops in the region. Tensions flaring after a U.S. Drone strike last week killed Iran's top military official, general qasem soleimani. In the heart of Iran a public outpouring of grief overwhelming the streets of its capital. Trump made a big mistake. He killed our hero. Reporter: Cries drowned out by angry chants. Soleimani, a beloved figure in Iran, seen as standing up to the west. Now his death and the way it was carried out a game changer for Iran and the United States. You don't have any right to kill him. Reporter: My colleague, Martha Raddatz, one of the few western journalists allowed in the country. This procession so packed you can barely move but the emotion is everywhere. People have a very strong message for America. Reporter: They're chanting "Death to America." Inside the funeral service, tears from Iran's supreme leader, ayatollah what mainny, Few figures were held in higher esteem by the Iranian people than Mr. Soleimani. He was the man who brought back pride. Reporter: On the ground his image everywhere. More than 1 million united in their cry for revenge. Revenge must happen, and it is certain. What kind of I venge do you want? Anything. Reporter: 24-year-old hussein is a college student. What is your message to I'm saying, we love Americans but we hate your president. Reporter: Soleimani, a critic of the United States, taunted president trump in a speech in 2018. Let me tell you, Mr. Trump, the gambler, know that we are near you in places that don't come to your mind. The U.S. Moved to kill the revered general, who command the elite revolutionary guard, proving consequential across the region. Members of the Iranian parliament chanting "Death to America." And this weekend an ominous sign, a red flag symbolizing war raised above an Iranian mosque. We took action last night to stop a war. We did not take action to start a war. Reporter: In the face of criticism, president trump insisted the attack was a necessary measure. Sol mainny was plotting imminent and sinister attacks on American diplomats and American personnel, but we caught him in the act and terminated him. Reporter: But there are questions about the administration's initial justification for the attack. Just how imminent those threats were. This evening the chairman of the joint chiefs of staff telling reporters the intelligence was compelling, adding -- Did it exactly say who, what, when, where? No. But he was planning, coordinating, synchronizing significant combat operations against U.S. Military forces in the region, and it was imminent. Reporter: But the Iranians deny those claims, instead pointing to the general's record of fighting ISIS. Reporter: Iranian officials threatening retaliation that would target U.S. Military in the region. Whether they punch back is a big calculus, because they know that if they do they're going to be hit hard with conventional attacks on Iranian soil. And those attacks could bring down a very fragile economy. Reporter: Over the weekend president trump warned if there is retaliation, he has 52 Iranian targets in his sights. Some he says at a very high level and important to Iran and the Iranian culture. A potential war crime under international law. But secretary of state Mike Pompeo telling ABC that no illegal action would be taken. Every target that we strike will be a lawful target, and it will be a target designed at the singular mission of protecting and defending America. Reporter: Trump contradicted that notion hours later telling reporters off camera that Iranians are allowed to kill our people, they're allowed to torture and maim our people, and we're not allowed to touch their culture sites? It doesn't work that way. Tensions in Iran impacting relations with neighboring Iraq. The Iraqi parliament angered at the killing of soleimani on their soil voting to kick the U.S. Out of their country. Amidst this crisis, the U.S. And nato pausing operations against ISIS. It's worth noting the last time there was a power vacuum in Iraq, ISIS filled the void. This latest round of escalations began in 2018 after president trump dismantled the Iran nuclear deal, brokered by president Obama. This was a horrible, one-sided deal. Reporter: Today the Iranian government announcing they're suspending commitments to that deal, now abandoning limits on enriching uranium and stockpiling nuclear fuel. Hostilities continue to escalate after a series of Iranian provocations over this past summer, including the downing of an American drone. Then in late December, an American contractor was killed in a rocket attack in Iraq. The U.S. Blamed an iranian-backed militia and responded with air strikes that killed at least two dozen people, possibly including civilians. On new year's eve, a huge crowd of protesters stormed the U.S. Embassy compound in Baghdad, breaching the highly fortified perimeter, a two-day siege sent diplomats into a safe room and forced Marines to deploy tear gas. President trump blamed Iran for orchestrating those protests. Ominously tweeting two days before general soleimani was killed, Iran is going to pay a very big price, this is not a warning, it is a threat. America's contentious history with Iran goes back decades, back to 1953, when the U.S. Installed the shah in order to protect oil interests. After 25 years, in 1979, mass demonstrations filled the streets and forced the shah into exile. Then just months later -- The U.S. Embassy in Tehran has been invaded and occupied by Iranian students. Reporter: Holding dozens of American hostages for 444 days. Before they were released in 1981. The relationship between the U.S. And Iran over the next few decades would remain fractured. Fast forward to 2013. President Barack Obama's administration started taking small but controversial steps to bridge decades of hostilities, including a one-on-one conversation with Iran's then newly elected president rouhani. In 2015, the U.S., along with a group of world powers, brokered the deal with Iran to end its nuclear program. That momentary thawing of tensions now history. What happens next, unknown. And we'll have much more coverage continuing on "Gma."
This transcript has been automatically generated and may not be 100% accurate.