Hundreds of pro-Palestinian activists from the U.S., Europe and Canada are organizing a 10-ship flotilla to challenge Israel’s economic blockade of the Gaza Strip.

Israel says the blockade is necessary to prevent smuggling of arms into Gaza. Hanging over the mission is the dark shadow of last year’s flotilla that ended with an Israeli commando raid on a Turkish vessel and left nine activists dead.

The hub of this year’s operation is Athens, Greece, where organizers accuse Israel of using diplomatic pressure to sabotage their effort.

Some 50 American activists of Operation USTOGAZA are holding workshops in an Athens hotel. Over a year of fundraising throughout the country, the group raised nearly $400,000 to cover basic expenses and lease a boat.

One of the most prominent American participants in the flotilla is Pulitzer Prize winner Alice Walker, author of The Color Purple.

She gave her reason for taking part in a video on the group’s website: “I actually love children and I love water, and I love trees, good food, and I love parents who are happy and children who are happy and all this wonderful life that has been completely disrupted and degraded by the Israeli treatment of the Palestinian people in Gaza.”

The American vessel has been renamed The Audacity of Hope, after the title of President Obama’s autobiography. But organizers won’t reveal where it’s docked, or when they’ll set sail. They claim Greek authorities have imposed administrative delays under pressure from Israel.

But it’s not just Israel that opposes the flotilla. Despite its opposition to the blockade, the Greek government has officially urged its citizens and Greek-registered vessels not to participate in the operation.

U.N. Secretary-General Ban Ki-moon said aid should be delivered to Gaza only through what he called legitimate crossings and established channels — meaning through Israel or Egypt.

The Obama administration has also strongly urged U.S. nationals not to take part.

Ann Wright, a retired State Department official and former army colonel, took part in last year’s attempt to break the Gaza blockade.

“Israelis have been very clear: They intend to stop us from going to Gaza and will use force,” Wright says. “We will not use force. We are unarmed civilian ships that are sailing for a political purpose to bring world attention to what is going on in Gaza.”

The Americans — whose ages range from the mid-20s to mid-80s — say their ship will carry only written messages and letters to the Palestinian people. Other ships — from Europe and Canada — will carry various goods, from medical supplies to school notebooks.

Activists see Israel’s Gaza blockade as a human rights violation, while Israel says it’s aimed at preventing weapons from reaching Iran-backed Hamas militants.

Last year’s attempt to break the blockade was intercepted by Israeli naval commandos and resulted in the deaths of nine activists.

The Americans in Athens have trained for their voyage by watching graphic videos of that raid. Richard Levy, a civil rights lawyer, took part in the nonviolence training.

“We put in a number of hours learning how to respond to that kind of an assault,” Levy says, “and I guess most of us on the boat are sailing with the recognition that that is a real possibility and how do we best protect ourselves under those circumstances.”

In another hall of the hotel, a group of women wearing T-shirts with the words “I am an unarmed citizen” and “Stay human” is discussing possible scenarios.

Medea Benjamin is the founder of Code Pink, a women’s anti-war group.

“Some of us are Jews; we are certainly not against the Israeli people,” Benjamin says. “Our idea is we are part of a historical movement that has deep roots in Gandhi, deep roots in Martin Luther King, deep roots in civil resistance movements throughout history.”

The American activists alternate their training with song sessions — to the tune of “Michael, Row the Boat Ashore,” they’ve adapted the lyrics to their Gaza mission.

On Monday, the Israeli government said it would act with determination to stop the flotilla from reaching its destination, but, it added, with minimal confrontation, as far as possible, between Israeli forces and passengers.

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