The Big Question: Is there any hope that the last surviving Nazis can be brought to justice?

Why are we asking this now?

Because the Simon Wiesenthal Centre, a Jewish human rights group which has brought hundreds of Nazi war criminals to justice since the end of the Second World War, has just launched a campaign called "Operation Last Chance". It is being run by Efraim Zuroff, the new head of the Wiesenthal Centre who points out that as the Second World War ended over 60 years ago, the remaining Nazi war criminals still alive are now so old that they may die before being brought to justice. He says the world has a "last chance" to catch them and bring them before the courts. The campaign will involve a media campaign and the offer of financial rewards for information leading to the arrest and prosecution of the suspects.

How many people are we talking about?

Hundreds ranging from Nazi concentration camp guards who beat their prisoners, to a handful of big-time Nazis who were responsible for mass murder and brutal torture. In Eastern Europe there are an estimated 488 Nazi war crimes suspects. Between 150 and 300 fled to South America and some Middle Eastern countries after the war, though no one knows how many are alive.

Who are the chief targets?

The last remaining major Nazi war criminals are Austrian-born Dr Aribert Heim, who is wanted for the murder of hundreds of Jewish prisoners at the Nazis' Mauthausen concentration camp where he worked as a doctor in 1941, and Alois Brunner, a close aide of the convicted Nazi war criminal Adolf Eichmann, who invented a mobile gas chamber used on thousands of Jewish prisoners. Heim ranks alongside infamous Auschwitz death camp doctor Josef Mengele as one of the Nazis' worst individual war criminals. A court trying him in his absence in 1979 said he "wallowed in the fear of death suffered by his victms" while performing lethal operations on them without anaesthetics.

Where are they?

Brunner, now 93, was recently spotted and photographed in Syria where he lives under an assumed name. Repeated attempts to extradite him have failed. Heim's lawyer, Fritz Steinacker, may know his whereabouts, but claims that revealing such information would breach Germany's client-lawyer secrecy legislation. There have been several alleged sightings of Heim in Egypt, Spain, Germany and South America. He has been on the run since the 1960s when Germany issued his arrest warrant.

Why did the arrest warrant take so long?

Like many war criminals, Heim managed initially to cover up his wartime activities. He worked for years as a gynaecologist and later as an army doctor after the war. He married and lived undetected near Frankfurt, where he played in the local ice-hockey team. The Austrians opened an investigation in 1957; the Germans followed in the early 1960s. Nazi colleagues are believed to have tipped off Heim just before police arrived to arrest him. He drove away in his Mercedes and has evaded capture ever since. Two years ago, German state prosecutors announced that he was at the top of their list of wanted Nazi war criminals.

Where are the Nazis hiding?

Eastern Europe is one area which is believed to be home to Nazi war criminals. The Simon Wiesenthal Centre launched a Nazi-hunting operation there in 2002 and came up with the names of 488 Nazi war-crimes suspects. Ninety nine cases have been submitted to local prosecutors. However, only three arrest warrants and two requests for extradition have resulted from that campaign, though scores of cases are still under investigation. Alois Brunner is still being afforded sanctuary in Syria. South America, where Operation Last Chance was launched earlier this week, has been a favourite haven for Nazi war criminals. In Argentina in the 1960s, President Juan Peron's government organised missions to rescue Nazi war criminals from post-war Europe after branding the Nuremberg war crimes trials as "infamy". Scores of unrepentant Nazis were given top jobs under assumed names as technicians in the Argentinian armed forces. Right-wing military dictatorships in Paraguay, Chile and Uruguay have been other havens. In the Middle East, anti-Israeli circles have given sanctuary to Nazis.

Are any still in Europe or the US?

Yes. Even 60 years after the Second World War, war criminals are found to be living in Europe and the US. Organisations like the Simon Wiesenthal Centre say that there is a new readiness to track down Nazis in South America because many countries there are now full-blooded democracies. However, the organisation complained only last year that countries such as Austria, Germany and Poland had an abysmal record of bringing suspected war criminals to justice. In Germany, ex-Nazis wanted for war crimes committed outside the country do not have to be extradited under existing laws.

What have efforts to find Nazis achieved?

Apart from the Nuremberg war crimes trials, which were conducted by the Allies immediately after the Second World War, there have been some spectacular catches of Nazi war criminals. One of the biggest involved the capture of Adolf Eichmann, one of the masterminds of the Nazi Holocaust. He organised the transport of millions of European Jews to the death camps, but fled to Argentina after the war. However, in 1960 he was kidnapped by Israeli secret agents and taken to Israel where he was put on trial, convicted of war crimes and executed in 1962. Other big catches include Klaus Barbie, a Nazi Gestapo chief nicknamed the "Butcher of Lyon" who was tracked down in South America and stood trial in France in 1987. Franz Stangl, commandant of the Treblinka death camp in Poland, where only 40 out of over a million prisoners survived, was extradited from Brazil and sentenced to life imprisonment in the then West Germany in 1970.

And the failures?

Josef Mengele, the Auschwitz concentration camp doctor who performed brutal medical experiments on inmates, died in Brazil in 1979 after spending most of his post-war years living with impunity in Argentina. Eduard Roschmann, the so-called Nazi "Butcher of Riga" who was blamed for the death of 40,00 Jews in Latvia, died in Paraguay in 1977. He never faced a trial.

Will Operation Last Chance result in more Nazis being put on trial?

Yes...

* If enough people come forward with information which leads to their arrest and South America's democracies show willing

* If the financial rewards for doing so are big enough

* If the major criminals still out there such as Heim and Brunner are still alive if and when they are eventually caught

No...

* Countries such as Syria continue to harbour suspected criminals

* Often in recent years, many Nazi war crimes suspects are judged to be too old and infirm to stand trial

* Operation Last Chance could have already missed the boat if it turns out that the majority of Nazi war criminals are already dead