Osthoff, 43, is a Bavarian archaeologist originally from the Munich area who has spent decades studying and excavating sites in Iraq to uncover the secrets of ancient Mesopotamia, a region often referred to as the "cradle of civilization."
Osthoff had worked on a German excavation of the 4,000-year-old Isin site from the mid-1970s until the late 1980s, when UN sanctions forced most foreign experts out of the country.
In May 2003, two months after the United States and Britain invaded Iraq, Osthoff brought reporters to Isin to show them how Iraq's most important sites were being destroyed by looters.
"In two weeks, they have ruined all the work that was done over 15 years," Osthoff told The New York Times.
Osthoff's mother, in an interview with Reuters Television, said her daughter gave Iraq and its culture her "body and soul."
"She helped show the Americans what was happening to Iraq's cultural sites," Ingrid Hala said.
Shortly after midnight on Tuesday, Hala received news from the German foreign ministry that Osthoff had been kidnapped in Iraq and was being held by gunmen. They were threatening to kill her if Germany did not end its cooperation with the Iraqi government.
An image from a tape brought to German state broadcaster ARD showed two blindfolded people sitting on the ground surrounded by three armed, masked men. One held a rocket-propelled grenade launcher; another read from a piece of paper.
The fate of Margaret Hassan?
Germany's new Chancellor Angela Merkel has vowed to everything within her power to save Osthoff and her driver.
One German official told the Reuters news agency that they did not want her to end up like Margaret Hassan, a British aid worker who was kidnapped and killed last year by militants in Iraq.
Like Osthoff, Hassan spoke Arabic, had spent decades in Iraq and had devoted her life to the country. Hassan had also criticised both the pre-war UN sanctions and the invasion.
Osthoff witnessed Iraqis suffering during and after the war, which prompted her to turn to relief work. A converted Muslim, she began working as volunteer in Iraqi hospitals.
But like many foreigners in Iraq, where bomb attacks and kidnappings are commonplace, Osthoff lived in fear for her life and often travelled with armed guards.
Germany's Neue Osnabrücker Zeitung daily said in a press release that Osthoff told the paper in October she had been threatened by people close to the leader of al Qaeda in Iraq, Abu Musab al-Zarqawi, who has claimed responsibility for the murder of numerous hostages in Iraq.
Islam experts say the lives of Osthoff and her driver are very much in danger.Henner Fürtig of the German Orient Institute in Hamburg called the danger level "acute." Sonja Hegasy of the Berlin-based Modern Orient Center shares that view, adding however that the chances of a peaceful resolution to the crisis is greater than it would be if Osthoff were a national of a country that directly supported the US in the Iraq war.