In post-US Iraq, a growing Iranian threat

BRIAN WILLIAMS, anchor: So much has changed, of course, as a result of the almost nine-yearlong war in Iraq . One big change is this, while the Iraq of Saddam Hussein is gone into that regional vacuum now comes Iran , a neighboring nation, an enemy of the United States . Our chief foreign correspondent Richard Engel , who of course covered the Iraq War for close to a decade, tonight has gone back to examine the Iran connection.

RICHARD ENGEL reporting: To see what's changed in Iraq since the American war , just visit Baghdad 's holy shrine of Kadhimiya . It's an ancient Shiite mosque for prayer and meditation. Some worshipers are overwhelmed to tears. For Shiites this is all new. Shiite Muslims, the majority in Iraq , were oppressed by Saddam Hussein 's ruling Sunni minority, but the democracy America brought has turned the tables. Shiites are now in power here, and it shows. Kadhimiya has just undergone a $400 million renovation. Two hundred pounds of pure gold laid on each dome. But the biggest change for Iraq may be closer ties with its Shiite neighbor, Iran . These days, Kadhimiya is full of Iranian tour groups who come with their own guides with signs in Farsi . Under Saddam , no Iranians came to Iraq . Saddam was Iran 's enemy. Today more than two million Iranians visit Iraq every year. Iraq 's new dynamic is on display here every day. After nearly nine years, it's Iraq 's Shiites who have benefited the most. They have won this country. The United States toppled a dictator who's been replaced by a Shiite government with close ties to Iran . It's hard to imagine how that was ever part of the plan. Across town at Baghdad 's famous book market, Karim Hanoush , himself a Shiite, doesn't want US troops to leave.

Mr. KARIM HANOUSH:

ENGEL: He says Iran has calculated all this very well. They want a Shiite Iraq so they can control the assets, economy and politics. Fear of Iran 's growing power is sharper still in the Sunni stronghold of Fallujah . Once Iraq 's deadliest war zone , Fallujah remains violent. A bomb killed three policemen here just after we arrived. Police say Sunni radicals killed them because they work for the Shiite government. Compared to other parts of Iraq , there's been little development in Sunni towns like Fallujah . This building was destroyed by US forces seven years ago and still looks like this. People here accuse the government of persecuting them, ignoring them, trying to cut Sunnis out of the new Iraq .

Unidentified Man #1:

ENGEL: A cloth merchant told me, 'You crossed thousands of miles from America . Why? If you want the oil, take the oil. If you want our money, take it. But you have destroyed life, the whole system.' US troops are ending their war in Iraq but this country is still at war with itself. Richard Engel , NBC News, Baghdad .