New York police arrested about 900 people in the first big crackdown on demonstrators since protests against the Bush Administration began late last week. Protesters fanned out across the city on Tuesday during the second day of the Republican presidential nominating convention.

The War Resisters League called for a day of civil disobedience, beginning with a vigil at Ground Zero. Members then planned to march north to meet more participants on their way to stage a so-called die-in in front of Madison Square Garden, the site of the convention. Their plans were to lie in front of the convention center in a visual expression of the war dead and wait to be arrested.

Jim Morgan waited for the group at a location midway along the march route. He says opposition to the war in Iraq is not his only motivation in protesting.

"I happen to live in such a way that I come into daily contact with disadvantaged people. I am not," he said. "I see the burdens that people are carrying because of the way the government has carried out its service, if I can use that word, over the last four years."

Mr. Morgan did not get to join the march because police arrested at least 200 members of the group at Ground Zero, encircling them with netting and loading them onto buses. They are being charged with blocking the sidewalk.

Other protests throughout the city espoused a wide variety of causes, ranging from campaigns against war to rallies for civil liberties and demonstrations for opponents of abortion.

Several hundred people held a demonstration protesting post-9-11 policies that allow the government to detain individuals who are considered a threat.

"The ability to see what you are reading in the library, the ability to get federal search warrants without going through a due process, the ability to hold people, including US citizens, if they are designated enemy combatants, which is just a made up term," said Jess Duritz, who organized the protest. "You can hold them, they cannot have visits from a lawyer. They cannot have visits from their family. In some cases, we don't even know where people are. It is scary stuff."

Others protested against the Halliburton corporation, the company Vice President Dick Cheney used to head, which has won many reconstruction contracts in Iraq.

"We don't agree with their way of making money off this war. You hear four more wars back here," said Mandeep Gill, who joined the demonstration. "They are saying that because they are mocking the idea that we are going in to liberate a country. I think we are just going in to make money for big corporations."

U.S. postal workers took to the streets in a rally near the convention site against what they call the Bush administration's plans to privatize the U.S. Postal Service.

"They wanted to privatize us, take our work and contract it out. We have had problems in areas where they are talking about consolidating some of our smaller facilities to the larger one," said one postal worker.

Since last week, police have arrested about 700 people for protest activities. The non-violent tone of the protests throughout the city was momentarily broken Monday night when a man beat a plain clothes detective, who is now recovering in the hospital. The action was caught on video and city officials are requesting help in identifying him.