Step by step, along the roads of Iraq, millions of people of all ages – men, women and even little children – have been walking over the last two weeks in devout pilgrimage.
Their goal is to reach the holy city of Karbala, in south central Iraq, by Thursday for one of the holiest days in the Shiite religious calendar, called the Arbaeen, which commemorates the seventh century martyrdom of Imam Hussein, the grandson of Prophet Mohammed.
The pilgrims face many dangers on their slow journey through a country where civilians are always an easy target for terrorism.
"Over the last 10 days, no fewer than a million people a day have already marched into Karbala," the city's governor, Aqeel al-Khazaali, told the Iraqi newspaper Al-Sabah.
Many of those pilgrims have already visited the shrine in Karbala and returned home, but the largest concentration of people is expected later this week.
"The biggest crowd will be between Wednesday night and Thursday morning, when at least four million pilgrims will be in the city at the same time," Al-Khazaali said.
In order to reach their destination, the pilgrims spend days and nights in the streets, where they are fed and cared for by people living in the towns and cities they pass along the way.
The people feeding the pilgrims are in most cases complete strangers who the marchers have never met before, and who ask for no payment, but spend their own money on hot meals and warm beds just to help the marchers continue their journey.
They believe their charitable deeds will be acknowledged and rewarded by Imam Hussein when they reach heaven in the afterlife.
Iraq's Shiites, who make up more than 65 percent of the population, believe that marching to Karbala is a necessary part of their devotion to God.
One policeman in Nassariyah, in southern Iraq, told ABC News, "I asked my supervisor for one week's leave in order to march to Karbala because last year I vowed to God that if I was able to get a job I would make the pilgrimage to the shrine of Imam Hussein."
Another marcher, an elderly man wearing threadbare clothing and shuffling along the road to Karbala, told ABC News: "I want to go just so that I can ask Allah to bring peace to Iraq."
It is well known among the Shiites that harming the pilgrims of Imam Hussein is very sinful and the person who thinks of doing so will be cursed all his life.
So the pilgrims travelling from the south, up through majority Shiite areas, are relatively safe in their journey.
But Shiites living in other parts of the country, like Baghdad, who need to march through ethnically mixed areas – especially ones where al-Qaeda fighters are still active – are more fearful for their lives.
Because of this danger, Iraqi police and army soldiers are providing some security through a series of checkpoints and patrols along the way; many within sight of each other.
But despite these measures, at least 70 pilgrims have died on Sunday and Monday, including a suicide attack that killed 65 in Iskandariya on Sunday.
Iraqis who march to Karbala carry a lot of personal hopes in their hearts, but above all peace and prosperity to all parts of Iraq.