As troops from France, Italy, Spain, Turkey and other donor nations prepared to deploy in southern Lebanon, Germany’s late decision to participate ranked as its most delicate foreign policy move since it was held to account for the Holocaust in 1945. Since then, it has been unthinkable that Germans would put themselves in a combat situation in which their soldiers could shoot at Jews.

The decision to deploy troops to join the 15,000-strong Unifil peacekeeping force was made by Angela Merkel, the Chancellor, in consultation with three Cabinet ministers. They agreed to take on such a role in their first venture into the Middle East because of the difficulties of recruiting enough properly equipped peacekeepers for the mission.

“We have to do this, not in spite of the Holocaust, but because of it,” Werner Sonne, a leading commentator, said on German state television. “If German troops guard Israel’s borders, they are there to protect Jewish lives. Frankly, there has never been a better reason to bring in soldiers in German uniform.”

That set the tone yesterday of what promises to be a huge national debate, not only about Middle East policy but about how the Nazi past should inhibit Germany’s expanding role in world politics.

Frau Merkel seems ready to send some 3,000 troops, of whom about 1,000 will be Pioneers with heavy earth-moving equipment to help to rebuild airports and harbours. The navy, already in the eastern Mediterranean on Operation Active Endeavour, would be strengthened with frigates to patrol the coast of Lebanon.

The German Air Force is being put on stand-by to fly reconnaissance missions from Cyprus and the German Border Service could be put on patrol along the Lebanese-Syrian border to stop the transfer of weapons to Hezbollah. German soldiers could find themselves drawn into a firefight in any of these theatres.

France will command the force with lead elements arriving in the coming days. The French appear ready to send 5,000 soldiers, Italy 3,000 soldiers and Turkey a further 1,500. German diplomats say that one priority is to convince other Muslim countries, such as Malaysia and Indonesia, to commit troops as well.

Unifil is supposed to patrol the rugged region of southern Lebanon from the Israeli border north to the Litani river, an area dominated by Hezbollah.

The peacekeepers intend to offer support to 15,000 troops from the Lebanese Army. Last night the UN said it hoped that up to 3,500 of its peacekeepers would be in Lebanon within two weeks.

Hezbollah remains the most powerful military force in Lebanon and Sheikh Hassan Nasrallah, its leader, dismissed any suggestion that his men should lay down their arms. The danger for the peacekeepers is that the ceasefire will break down and tit-for-tat attacks resume, leaving them with the choice of using force against the Israeli military or Hezbollah fighters, or doing nothing.

Germany has been encouraged to send a big contingent by the Israeli Prime Minister, Ehud Olmert, a sign that the Holocaust taboo is beginning to crumble. In an interview with the German newspaper Süddeutsche Zeitung this month, Mr Olmert said he had told Frau Merkel that Israel had “absolutely no problem with German soldiers in southern Lebanon”.

“There is at the moment no nation that is behaving in a more friendly way towards Israel than Germany,” Mr Olmert said. “If Germany can contribute to the security of the Israeli people, that would be a worthwhile task for your country. I would be very happy if Germany participated.”

Yet some German observers believe that a degree of calculation lies behind the Israeli enthusiasm. In a fast-moving exchange of fire, German soldiers might give the Israelis the benefit of the doubt.