Returning to Paris in January 1940, he wrote "Über den Begriff der Geschichte" ("On the Concept of History", later published as "Theses on the Philosophy of History"). While the Wehrmacht was pushing back the French Army, on 13 June Benjamin and his sister fled Paris to the town of Lourdes, just a day before the Germans entered the capital with orders to arrest him at his flat. In August, he obtained a travel visa to the US that Horkheimer had negotiated for him. In eluding the Gestapo, Benjamin planned to travel to the US from neutral Portugal, which he expected to reach via Francoist Spain, then ostensibly a neutral country.
The historical record indicates that he safely crossed the French–Spanish border and arrived at the coastal town of Portbou, in Catalonia. The Franco government had cancelled all transit visas and ordered the Spanish police to return such persons to France, including the Jewish refugee group Benjamin had joined. They tried to cross the border on 25 September 1940 but were told by the Spanish police that they would be deported back to France the next day, which would have thwarted Benjamin's plans to travel to the United States. Expecting repatriation to Nazi hands, Benjamin killed himself with an overdose of morphine tablets that night, while staying at the Hotel de Francia; the official Portbou register records 26 September 1940 as the date of death. Benjamin's colleague Arthur Koestler, also fleeing Europe, attempted suicide by taking some of the morphine tablets, but survived. Benjamin's brother Georg was killed at the Mauthausen-Gusen concentration camp in 1942. Despite his suicide, Benjamin was buried in the consecrated section of a Roman Catholic cemetery.