During the most violent years of the Iraq war, American commanders believed that neighboring Iran was behind insurgent attacks -- a way to keep the country unstable.
As U.S. forces slowly depart Iraq, officials say Iran is moving toward a more soft-power approach, trying to influence politics, social services and the economy.
One of the most sacred places in the world for Shiite Muslims is the shrine of Imam Ali in Najaf, Iraq. Ali was the cousin and son-in-law of the prophet Muhammad.
Women young and old crowd up to the golden casket where Ali is thought to be entombed. They touch it and kiss it, begging Ali to grant their prayers.
During the rule of Saddam Hussein, very few Shiites from outside Iraq could visit, but now more than a million come each year, and most are from Iran.
Religious tourism is big business in Iraq, second only to oil exports.
Saeb Radhi's hotel is a main stop for Iranian pilgrims on their way to the shrine. The first thing visible in the lobby is a prayer room.
"Of course in the past it used to be a reception," Radhi says. "My special office was here, but we made it as a praying place for them."
Them being the nine tour companies that bring Iranian pilgrims to Iraq.
These companies control everything, Radhi says, from what TV channels each room should provide to the catering company that prepares Iranian food and delivers it to the hotel.
Radhi and other hoteliers complain that the companies were hand-picked by Iranian officials who control religious travel. Each one of the companies, they say, is connected to a political party in Iraq.
"So if it is a matter of tourism only, so why only nine companies have to run this business," Radhi asks. "Why not other private companies? For instance, I've got a company, he's got a company. So why you can't run the business? Why only these nine companies can run this business?"
It's not just tourism companies here that are controlled by Iran.
"This is the hospital -- you see it says Islamic Republic of Iran," says Radhwan Kilidar, a former member of parliament from Najaf.
He points out Iranian construction projects around the city. Some are public, such as the Iranian consulate. Others, including the office of an Iranian cultural organization in Kilidar's neighborhood, are more discreet.
Kilidar says when the U.S. first toppled Saddam Hussein, Shiites in southern Iraq welcomed Shiites from Iran. But when it seemed that Iran was meddling in Iraq's affairs, people grew suspicious.
Now, Kilidar says, he doesn't mind Iranian pilgrims, Iranian goods or Iranian expertise. Iranian exports to Iraq are expected to hit $10 billion a year.
"When there's political motives behind such things, we say no, we'll put a stop and let's think about it again," Kilidar says.
Just because Iran is flexing its power doesn't mean it always gets what it wants, says Joost Hiltermann, an Iraq analyst with the International Crisis Group. For instance, Iran's hope that a super-Shiite bloc would dominate Iraqi politics is not coming to pass.
Iran's arch-enemy, the United States, is pulling its troops out of Iraq. And that, Hiltermann says, means Iran's role in Iraq is changing.
"It will no longer need to play the role of spoiler in Iraq that it has been playing over the past seven years," Hiltermann adds. "It's not in Iranian interest that Iraq fall apart. That requires a positive task of nation-building."
Hiltermann says this task puts Iran's interests much closer to those of the U.S. He says the old proxy war between the U.S. and Iran is ending, and a new relationship between the two could begin.