The distinguished Salvadoran jurist lived in Europe for many years in his career as a diplomat and as presiding judge of the Permanent Court of Justice International, based in The Hague, The Netherlands.

[citation needed] In 1937, during the rise of Nazism in Europe, Doctor Guerrero took over as president, until he was forced to leave in 1940 by the Nazis.

Precisely after the fall of Holland, on May 17, 1940, the Nazis tried to take the Palace of the Permanent Court of Justice in The Hague, but there they met the Salvadoran, the only judge who stayed with a group of Dutch officers.

However, now it was part of a larger project: the handing over of false documents of Salvadoran nationality to people of Jewish origin Castellanos then consulted Dr. Guerrero, who immediately agreed to that plan that saved the lives of thousands of Jews.

[citation needed] In 1945 San Francisco, California, a conference was held attended by more than 50 countries and on which the United Nations Organization (UN) was founded.