This was three weeks into the Israeli invasion of the West Bank, the third invasion in six months. The centre of Bethlehem was deserted, and the air was filled with the smell of meat and vegetables rotting in the refrigerator plants of the market, a market that had been comprehensively vandalised by the soldiers. The smell joined with others, from the refuse that was tied in bags and dropped out of windows to remain, uncollected, in the street, and from drains that had been fractured by the weight of the Israeli tanks; when it rained, as it did often that Easter, the raw sewage swilled out into the street.

The soldiers were young, armed and tanned. In their wraparound sports shades, they looked as though they had come to the invasion straight from a skiing holiday. But they shrank before Adam and Huwaida's questioning: why were they there; why were they choosing to follow illegal orders; why were they blocking all attempts to deliver food to families who had been forbidden to leave their homes for the past 17 days?

Ostensibly, I was doing the same thing as Adam and Huwaida: delivering food and medical supplies to Palestinians under siege. I had followed my Palestinian wife to Bethlehem as she made a film about the International Solidarity Movement (ISM), a coalition that Huwaida had founded the previous summer, alongside members of two Palestinian foundations with strong international ties, the Holy Land Trust and the Rapprochement Centre, one Christian, the other secular. The inaugural meeting also included an Israeli woman named Neta Golan who already campaigned under the name ISM. As Neta's group comprised only three women, it was felt the new movement could adopt her name.

Adam was working for an American foundation named Seeds Of Peace which required him to keep out of politics, so in the beginning his role in ISM was, he says, "logistic". "I typed press releases and I helped with funding." Fundraising? As I ask, he laughs. "No. From my own pocket. I was the only one with a job."

The ISM was founded with the aim of strengthening peaceful protests against the Israeli occupation. The feeling, back in 2001, was that the presence of foreigners would deter the Israeli army from using lethal force and give ordinary Palestinians the confidence to take part in protests, a confidence that had been lost since the early days of the first intifada. A year later, as we reflect on that Easter, Huwaida says, "We had planned all kinds of direct action. We were going to be proactive, highlighting closures and planning on marches and dismantling roadblocks. And then the invasion happened. Even the international agencies were stopped cold." The ISM's work became chiefly humanitarian. "That's when we started putting people into ambulances and calling up the army directly to say, listen, there are foreign volunteers inside those ambulances," she says.

"Our work changed because the UN and the Red Cross were failing the Palestinians," says Adam. "Their mode of operation is to liaise with the Israeli army and if the army refuses to cooperate, there is nothing they can do."

The invasion began on Good Friday, March 29 2002, in Ramallah. Adam and Huwaida had made their home in the city soon after the founding of the ISM and they woke, with the city lashed by storms, to find a tank parked outside their building. Adam and an Irish woman named Caoimhe Butterly volunteered to ride the ambulances. "The ambulances were being shot at," Adam recalls. "They were being stopped for long periods and ambulance drivers were being arrested. I remember we picked up corpses and took them to the morgue. We helped a pregnant woman and moved a kidney patient on dialysis from one hospital to another. But we were hearing that there were injured people in the presidential compound. So Caoimhe and I decided to go."

When they got to Yasser Arafat's compound, they were fired on. "I picked up the megaphone and started to explain why we were there - that we wanted to bring people out. That led to three hours of negotiation... eventually, they let us in."

Adam's presence in Arafat's headquarters was immediately reported in the American press, which led a columnist in the New York Post to label him "the Jewish Taliban", after John Walker Lindh, "the American Taliban" who was discovered fighting in Afghanistan.

Adam explains that he and Caoimhe had never intended to stay inside the building; they both planned to leave in ambulances. But they were trapped in the presidential compound by the soldiers. Overnight, the Israeli tanks pounded the building. "There were more than 300 inside, officials and security personnel. Food was running low. There were elderly people with medical conditions. The water was cut, the electricity and the phones. The toilets were pretty bad. The shelling was continuous. No one inside returned fire, but they made clear they intended to fight if the building was invaded."

Huwaida was on the outside. "I had been thrown into a coordinating role. I was asking myself, 'What do we need to do now?' I was trying to think strategically under extreme pressure. I had utmost faith in Adam, but at the same time, it was very frightening. There were all these armed men inside and he was saying that, if the compound was attacked, then it would be a bloodbath." She contacted the US special envoy, General Zinni, and the ambassador, Aaron Miller. "I got through about two in the morning, and he asked me, 'How would it be if we could get Adam out, with no pre-conditions - would he go?' I told him, 'He went in to help people, so I don't know if he would agree.' And then we were told, 'You know, we can't help.' "

By Saturday morning, Huwaida and Neta Golan had decided to stage a mass march on the compound by ISM volunteers, men and women who had come to Palestine to take part in the original programme of peaceful marches and protests, but who now found themselves in a war zone. "We got an ambulance and 70 people together, and the march began at midday. The soldiers stopped us, but eventually we compromised and they allowed in one ambulance and two doctors, and Adam came out and one doctor stayed."

The invasion would last for more than 40 days. In a second march on the presidential compound, Neta Golan and other ISM volunteers joined Caoimhe inside. "The intention was to force a negotiated settlement," Huwaida says. "At this point, no other city had been invaded." That came two days later, with the invasion of Bethlehem, followed by Nablus and then Jenin. Earlier, at a peace march in Bethlehem, an Israeli soldier opened fire on a group of 100 American and European volunteers, which included the comedian Jeremy Hardy, my wife and me, as well as the BBC and other news crews. Most of the bullets ricocheted off the ground and surrounding walls, but a few, judging from the injuries they caused, appeared deliberate. This was chilling notice that the ISM could no longer assume the army would not use lethal force against foreign nationals. The official Israeli explanation was that the soldiers were firing warning shots.

As the Israeli momentum slowed at the end of April, Adam returned to America to publicise his work in the West Bank. The trip home was emotional. The New York Post's description of Adam as the Jewish Taliban had been taken up by newspapers across America, and websites were decrying him as an apostate and a pig. His family home was threatened by local chapters of Betar and the Jewish Defence League, groups on the extreme right of pro-Israeli opinion, forcing his parents out of their house; meanwhile, his lawyer brother was put under 24-hour guard by the mainstream Jewish Anti-Defamation League, to protect him from extremists.

Adam's parents were unstinting in their support. "My parents felt a general affinity for Israel, although they never went there. When I engaged with the issue, it wasn't a major trauma for them to find out what the situation was really like. To the extent that the occupation is being done in their name, they are not happy and so they have become more active. They genuinely want to see an end to the violence for everyone." Where Adam disagrees with his family, and the majority of world Jewry, is in his view of Judaism. "I don't identify as Jewish. I see it as a religion rather than an ethnicity and, as I have no religious feelings, I don't regard myself as Jewish. I know many other people have a different understanding. I am the only one in my family who sees it that way."

Adam's faith, or lack of it, was a concern to Huwaida's father, too. As a devout Catholic, from a small Christian village in Upper Galilee in what is now Israel, he had always made clear that he would not want his children to marry outside the faith. And he was particularly uncomfortable with the implications of his daughter marrying a Jewish man. He and his wife had left Israel in 1975, when they were in their 20s, and despite his family's entreaties, he had not wanted to return to live as a "second- or third-class citizen", as Huwaida puts it. "My father had not come across any Jews who defended Palestinian rights. He grew up oppressed by a people who, under Israeli law, had more rights to his land than he did. Adam's family in America have more rights to his land than he does."

The knowledge that her father could not look kindly on their relationship would cast a shadow from the beginning. But the beginning had been a long time coming. The pair first met at Seeds Of Peace in Jerusalem, where Adam was Huwaida's boss. He had worked for the foundation since 1997, in New York, and when a youth centre was established in Jerusalem in 1999, he took the job of director. She began work there in 2000 as a programme coordinator.

"She didn't like me," Adam says. "She was kind of cold."

"I didn't hate him. Though he thought I did. I think the problem was, we have very similar personalities, so we didn't seem approachable. But I was never actually conscious of throwing him dirty looks." She pauses. "You know, maybe there was an attraction."

Seeds Of Peace is an American foundation that promotes dialogue between children from conflict zones; initially those from Palestine and Israel, though it later branched out to include those from the Balkans and Cyprus. After university, Huwaida had worked in Washington for an Arab-American lobby group. She took the Jerusalem job with Seeds Of Peace despite some reservations. "The problem is not that we cannot speak together, the problem is the occupation." She already knew Jerusalem well, having studied at the Hebrew University as part of her degree course at Michigan University. And she had been visiting the country since she was a child. Huwaida was born in February 1976, the year after her parents emigrated to Detroit, yet she holds Israeli citizenship.

As Huwaida worked with Adam, and listened to him debate in meetings, he gained her respect. It became apparent that he shared her views on the limits of the Seeds Of Peace philosophy. And Huwaida's own views were crystallising. "It's not that I didn't believe in dialogue. But there was this desperate escalation and I thought people should take to the streets. When I began to go on demonstrations, I had to promise to keep my name out of the press and my ass out of jail." And she was impressed with the patience and care he showed to the children. "In my relationship with Adam, one kind gesture led to another." She recalls a convention in Prague for the children of the Cypriot conflict. "We had to take a later flight and he offered me dinner. I think he was shocked that I accepted."

A week later, they were working late and Adam was upset over a work argument. "I asked him if he wanted to talk. He was surprised I cared. That was the night we had our first kiss."

From very early on, Huwaida had made clear that the relationship could not go far without their making a serious commitment: "There was the religious issue and I told him my father would not approve." But the tensions only added impetus to the relationship. By this time, both had left Seeds Of Peace and were working full-time for the ISM. It was June 2001, Adam says, when he asked her to marry him. Huwaida disagrees. "He didn't ask per se . It was late one night and I had dozed off when he said he thought it would be a good idea if we got engaged. I came to just as he was asking me what I thought, and I said, 'That's cool, honey.' He was a little surprised, so the next day he asked again what I thought and I said, 'About what?' "

Huwaida eventually stayed awake long enough to understand Adam's proposal and in July, when Huwaida returned to the States, she asked her father if he would speak to Adam. She says, "At first he was opposed to even meeting Adam." Was she nervous? "I was nervous but I was also excited. I knew my family would have to love Adam." As soon as her father agreed to a meeting, Huwaida called Adam in Jerusalem and told him to get on a plane.

"I was in Detroit for only 24 hours," Adam says. "I flew out specifically for that." Was it a long meeting? "No. One hour, an hour and a half." Adam is circumspect about details, but Huwaida says, "I think my father had a hard time distinguishing between being Jewish and Israeli. He asked Adam if he had served in the Israeli army and Adam said, 'No, I'm American', but my father asked the same question in three or four different ways." Huwaida's father was a long time giving an answer, under pressure not only from his immediate family (Huwaida is the eldest of four, three girls and a boy), but also his family in Israel. It was four months later that he finally gave his permission, and the two families came together for a Thanksgiving dinner. Adam says, "After that, it really was not a problem. They all just hit it off. We got engaged two days later in a short ceremony at the church. The priest said a couple of prayers and blessed the rings. I had been told to agree to get married in a church and I said, 'It's not a problem.'"

The wedding was set for late spring the following year but, as the day drew near, it seemed that it might never happen. This time, the problem was not Adam. It was Huwaida. He had returned to the US at the end of April for a conference; she was still in Palestine. "The last time we saw each other, I don't want to say we had an argument, but it got heated. Adam didn't want to leave. He was saying, 'I don't believe you are going to meet me for our wedding.' I got very upset. I was saying, 'Don't tell me I will stand you up.' "

Adam had every reason to fear she would not show up.

The wedding was set for May 26. By early May, the Israeli invasion of the Palestinian areas had resolved itself into two sieges: at the presidential compound in Ramallah and at the Church of Nativity in Bethlehem. While Bethlehem remained under 24-hour lockdown, the Palestinian coordinator of ISM was forbidden to leave his home. The job had been taken up by an English woman, Georgina Reeves, who was doing everything she could to get food and medical supplies to the men inside the church.

"We had tried to get into the basilica before, but this time the coordination was better," Huwaida says. It was May 2 and Georgina had maps of the area around the basilica, including sniper positions. In mobile phone conversations, the men inside the church agreed to remove their internal barricades and open the door as the ISM arrived. The soldiers were caught by surprise and, while Huwaida and others blocked the open door with their bodies, a number of volunteers took the food into the church.

The action was a huge morale-boost for the men, who were hungry and often felt they had been forgotten. A teenager who spent all 40 nights inside the basilica told me the cheering was so loud when the ISM arrived, he thought that Palestine had been liberated. There were no further assaults on the church once the ISM was inside, but the Israeli forces attempted to arrest the remaining ISM volunteers outside. "We sat down and refused to cooperate. Then I heard this voice say, 'You have to go, Huwaida, this isn't the University of Michigan any more.' " She turned around and looked up at a soldier. "He was an old classmate from university, and now he was serving in the Israeli army."

After the arrest, the men and women were separated. "We were cuffed and driven into Jerusalem," says Huwaida. The next day, assembled at the ministry of the interior, all those who refused deportation were thrown in jail. For Huwaida, deportation was unthinkable. Under Israeli law, anyone who has been deported cannot return to the country for 10 years; and so long as Israel controls all access to Palestine, deportation would mean the end of all further contact with her family and her struggle. Huwaida insisted she would leave only of her free will. And she backed it up with a hunger strike.

The hunger strike sent Adam into a fury. And as Huwaida had managed to sneak a mobile phone into prison, he let her know. "Adam was telling me to give up my morals and get married. My mom was crying every day." The problem was that Huwaida was even refusing water. This could seriously damage her health. Via the phone, her lawyers and her friends and sympathisers, Adam was leading a campaign to persuade Huwaida to change her mind, and after three days she began to accept water. But it was another three days before she received written confirmation that her demands would be met. She was not satisfied. There were still eight Americans in jail. "I demanded that everyone got the same letter. Finally, they gave in. They said, 'Now will you leave?' and I said, 'OK, I got a wedding to catch.' "

It was only on the plane that Huwaida discovered they had reneged on their promise. Two of the ISM volunteers spent a further 14 days on hunger strike. At the end, one of the men could not even lift his head. It seems that Huwaida was given the letter because of the legal problems involved in deporting her, when she holds Israeli citizenship.

"I actually made it back with two weeks to spare." Yet she and Adam continued to campaign, not least for the men left behind in prison. "There were so many interviews and speaking events that there was still no time for wedding plans."

"Huwaida's parents organised everything and all we had to do was turn up," Adam says. "This was good and bad. But it was mostly good."

"The dress was completely last-minute."

The wedding turned out to be far larger than Adam expected, with a sudden surge in well-wishers. "I think there were supposed to be 250 guests, but more than 300 showed," he says. "Detroit Radio announced the date, and after that we had complete strangers turning up."

"It was just a huge fun party," adds Adam. "Huwaida entered carrying candles, I just soaked everything in."

Even a headline in the New York Post, Jewish Taliban Weds, repeating the old taunt alongside a photograph of their wedding, failed to spoil the fun. Strange to say, when they returned to Ramallah after their wedding, Adam turned up in Jerusalem for a regular game of American football with American-Israelis and other Israeli friends, and they showed nothing but curiosity for his stance and actions. The truth is, Adam is far from being alone. The ISM in the US, at Huwaida's estimation, is one-quarter Jewish. Jewish volunteers on the ground in Gaza and the West Bank estimate that it may be as much as a third Jewish, a figure recently confirmed by journalists.

Yet since the invasion, the ISM's situation has become increasingly perilous. Caoimhe Butterly was shot in the same incursion that saw the fatal shooting of British UN worker Iain Hook. Then, in a short period of time in Rafah, ISM volunteer Rachel Corrie and Tom Hurndall, a young photographer working with them, received horrific injuries. Rachel died almost immediately. Tom subsists in a coma. Brian Avery, another ISM volunteer, lost half his face after being sprayed with shrapnel from a heavy machine gun fired at his feet.

I ask Adam if he feels responsible as he treks across the US, speaking and recruiting on behalf of the ISM. "Yes, I feel a responsibility. But we do everything we can do. We make contact with the army wherever we go. We absolutely never sneak up on them. We move in large numbers, making as much noise as we can. We have started wearing fluorescent vests. We have done everything we can do, but it is now that we have become targets."

Huwaida goes further. She believes that the Israeli forces have declared "open war" on the ISM. In a letter to the Guardian last Saturday, Shuli Davidovich, press secretary at the Israeli embassy, implicitly denies this: "The Israeli defence force takes the utmost care to ensure that innocent people are not hurt during their operations against terrorists who deliberately operate from within civilian populations. However... in war, tragedies do happen, as much as we would wish otherwise."

Huwaida's fear remains that the killings have been "legitimised" by recent claims from the Israeli army. A statement that a gun had been found in the ISM offices in Jenin was admitted to be an untruth. Huwaida says, "We took them to task and they retracted." A more damaging claim is that two UK-born suicide bombers "posed" as ISM volunteers. Of this, Huwaida says, "The idea that they gained any benefit by posing as ISM volunteers is ridiculous. Since April 2002, Israel has denied access to international peace activists."

The men are said to have spent a considerable time in other Middle Eastern countries before entering Israel. Adam asks if Israel intends to make the ISM responsible for everyone in the occupied territories. "They had three opportunities to detect these men - at the Israeli border, again as they entered Gaza and finally as they left Gaza," he argues. "If the stories about the movements of these terrorists are true, it's strange that Israel could not pick up on them. Israel degrades its own security by maintaining the occupation. They are stretching their resources, and it seems that security is not good."

Adam and Huwaida, and their story, bring into focus a national debate in America. And Adam thinks this will have a positive result. He is redoubling his efforts to attract hundreds of volunteers to the campaigns the ISM is organising for the summer. "With these kinds of numbers, we can be proactive and start to change some of the equations. The war has made many more Americans say, 'You know what, we have to make a stand now.' No government holds Israel to account for what it is doing to the Palestinians. Without the ISM, there would be no internationals in most of these areas. We simply have to be there."

"I was uncomfortable about the press covering the wedding," Huwaida says. And Adam has a strong sense of personal privacy, too. "But I tried to look at it another way, because people do find a positive message in it. That we can live together."

The problem is, they do not live together. Adam was arrested in Israel last summer, not long after the wedding, and deported. In the past year, he and Huwaida have spent only six months together.

"When we were planning our marriage, Adam said he wasn't getting married to spend all our time apart. But that's the way it has happened." And while she calls it a minor sacrifice, Adam sounds less sure.

"In some ways, it's easier when you're there, because you are active." He admits to finding life without her very difficult. "We communicate by text and email and phone. But some days we don't talk and that's nerve-racking."

"My mom asks about kids every day," Huwaida says, as they spend precious time together in Detroit. They have been touring the US giving talks, but today is May 11, Mother's Day, and they are at her family home. "I just heard my mother say I had promised her kids for Christmas. I was saying, 'When did I ever make that promise?' "

As we speak, their first wedding anniversary is a fortnight away, on May 26. Huwaida will be in the occupied territories. Adam will spend it in Washington, working on his PhD in peace and conflict resolutions. Either that, or watching his wife on CNN.

· Jeremy Hardy v The Israeli Army is at the Bloomsbury Theatre, London WC1, at 8pm on June 8. Tickets cost £7.50; box office 020-7388 8822.