In a last moment of calm before the climax of Martin Scorsese's new movie, "Gangs of New York," the Protestant and Catholic combatants bow their heads to pray. The familiar irony of the moment is that the warring parties have created difference out of what they hold in common. Scorsese's movie is the story of how the arrival of Irish immigrants after the Famine turned New York's desperately poor slums into battlefields, and the place of religion in those struggles.

But did Scorsese get his history right? We talked to Noel Ignatiev, author of "How the Irish Became White" about the racial, religious and economic divisions of the period, and found that the causes of the violence were even more painful than "Gangs of New York" shows.

Did you find the movie accurate?
A lot of the timing is wrong. The book the movie was based upon, Herbert Asbury's "Gangs of New York," written 80 years after the fact in the 1920s, did its best to sensationalize the actual events and the movie takes liberties with the book. A dramatist is entitled to do that, but we should judge the movie as drama and not history.

Bill Cutting, Daniel Day Lewis's character, was a nativist, an anti-immigrant. But he also seemed to be motivated by his Protestant faith. Did those things really go together?
Well, what motivated him was anti-Catholicism. It was not exactly religion, unless you call hatred of popery a religion. It's a kind of bigoted mainstream American Protestantism.

Were there nativists like Bill?
The character he's based on, according to the book, was killed in the 1840s, long before the movie takes place, and not in a brawl with Catholics, but in some kind of a sordid brawl among his own. But yes, there were Protestant-Catholic brawls in New York, Philadelphia, Boston and elsewhere. A convent was burned in Boston. There were riots in Philadephia, in which Protestants attempted to burn a Catholic church. These were anti-Catholic or anti-Irish. Sometimes it was just anti-foreigner, but it was mainly anti-Irish. It was more nativist than Protestant, but religion became a kind of fuel for it.

In New York, after the Philadelphia trouble, the Catholic archbishop said,"If anyone lays a finger on a church in New York City, they'll turn the city into another Moscow," referring to Napoleon's army burning the Russian city. So nothing got to quite the point in New York as it did in Philadelphia, but there were brawls.

They had largely subsided by the time of the Civil War, however, when "Gangs of New York" takes place. Even nativism had run its course. For a while, there was the nativist American Party--known as the Know Nothings--that lasted a couple of years in the early 1850s. But after 1856, the country was headed toward Civil War and slavery was emerging as the central question in American politics. I'm not saying everything was peaceful and harmonious between the Catholic Irish and the nativists, but it subsided.

How did all this lead to the Civil War draft riot that is the climax of "Gangs of New York"?
The Civil War riots were about the war, and particularly about Irish competition with black labor, which Scorsese scarcely alludes to.

The riots were sparked by the draft. But the background was the efforts by the Irish to secure a monopoly of jobs on the docks. As the Irish came in, they displaced black laborers in service trades, on the docks, barbering, waitering. The Irish simply underbid and pushed the blacks out, even in domestic service.

So there had been a lot of violence. There was a history of sort of mini-riots on the docks and elsewhere. In Brooklyn they burned down a tobacco factory because it was employing black laborers, and only allowed it to re-open when they agreed to employ Irish. In 1862, black workers were brought in to replace Irish strikers on the docks. So the riots were sparked by resentment against the inequities of the draft, but also because the Irish didn't want to fight a war to free the slaves, who they thought would come to New York and take their jobs.

If the fight was really between the Catholic Irish and the blacks, how did they end up brawling with the Protestant Irish?
The first wave of Irish came in the 1780, 1790s, and they were largely Protestant, and English-speaking. They weren't impoverished. The Catholics began coming after the economic dislocations at the end of the Napoleonic Wars. It really isn't until about 1830 that the Catholic Irish immigrants outnumber the Protestant Irish.

As this large number of Catholic Irish began coming-and they really were impoverished and disease ridden and prone to crime-the respectable Protestant Irish began to distance themselves from them. The analogy is the attitude of the old well-established German Jews from the 1840s and their immediate response to the large immigration of Eastern European Jews after 1890. There was a similar, lower-level phenomenon among well-established blacks in the North, in the face of the new black migration of the southern peasantry in 1917.