Of Irish descent, Donovan was born in Buffalo, New York, to Anna Letitia "Tish" Donovan (nee Lennon) and Timothy P. Donovan, both American-born children of Irish immigrants. The Lennons were from Ulster, the Donovans from County Cork. Donovan's grandfather Timothy O'Donovan (Sr.) was from the town of Skibbereen; raised by an uncle who was a parish priest, he married Donovan's grandmother Mary Mahoney, who belonged to a propertied family of substantial means that disapproved of him.

While British authorities and the US military and State Department were relatively indifferent to the question of trying war criminals after the war, Donovan was lobbying Roosevelt as early as October 1943 to arrange for such prosecutions. Roosevelt tasked Donovan with looking into the legalities and technicalities, and in the months that followed Donovan collected testimonies about war criminals and related information from a wide range of sources. In addition to seeking justice, Donovan wanted to exact retribution for the torture and killing of OSS agents. When Truman named Supreme Court Justice Robert Jackson to serve as chief U.S. counsel in the prosecution of Nazi war criminals, Jackson, discovering that the OSS was the only agency that had seriously explored the issue, invited Donovan to join his trial staff.  On May 17, 1945, Donovan flew to Europe to prepare for the prosecutions, and eventually brought 172 OSS officers onto Jackson's team, interviewing Auschwitz survivors, tracking down SS and Gestapo documents, and uncovering other evidence. Donovan, whose idea it was to hold the trials in Nuremberg, also introduced Jackson to useful foreign officials and even released OSS funds to bankroll the prosecution effort. Eventually, Jackson, who had been a political rival of Donovan's in New York State, considered him a "godsend"; in return for Donovan's help, but also because the OSS had proven "vital for the prosecution team," Jackson lobbied Truman in person to approve of Donovan's plans for a permanent postwar intelligence agency. The effort, however, was unsuccessful. On September 20, 1945, Truman signed an executive order abolishing the OSS.  In Nuremberg, Donovan interrogated many prisoners, including Hermann Goring, whom he spoke with ten times. But eventually Donovan fell out with Jackson. The latter wanted to indict the entire German High Command, not just men who had personally ordered or committed war crimes; Donovan considered this a violation of American principles of fairness. Donovan, a former prosecutor, also criticized Jackson's lack of skill and experience at putting together a strong case and at courtroom examination and cross-examination. Jackson removed him from the team, and Donovan returned to the U.S., where in January 1946 Truman presented him with the Distinguished Service Medal.

Using a quote from the above article, answer the following question: Who invited him?
Jackson, discovering that the OSS was the only agency that had seriously explored the issue, invited Donovan