As first American minister plenipotentiary to Poland in the chaotic postwar years from 1919 to 1924, he was called upon to respond to the acute problems of a renascent state while investigating reports of pogroms and mistreatment of Polish Jews.

He graduated from the prestigious École libre des sciences politiques in Paris in 1907 and entered the United States Foreign Service in his late twenties.

He did duty with Herbert Hoover, director general of relief, from November 1918 to April 1919 and was a member of the inter-allied mission to countries of the former Austro-Hungarian Empire, December 1918 – January 1919.

Assigned to the Round Valley Reservation on what had been Yuki Indian territory, he and his wife were horrified by the condition in which they had found the population and, according to a family tradition, went beyond their administrative duties to set up a school to teach their wards to read and write and to give them some idea of the outside world.

His wife, Mary Simons, trained as a schoolteacher, was also "a woman ahead of her time", says Diane C. Wood (p. 36-37), a political and educational activist, who "believed in birth control, a measure of sexual equality, Indian policy reform and world peace."

She sold the family home and with the proceeds took the 18-year-old boy on a tour of Europe in the course of which they visited Italy in a buggy and made prolonged stays in Berlin and Paris.

Gibson, as a neutral observer, traveled around Belgium (he witnessed and took pictures of the sack of Louvain), made his way through battle lines, and was sent on relief-related missions to Great Britain.

As reported by Hugh Wilson, who was in on the plot, Gibson, together with the members of his delegation strode into the room with solemn faces and addressed the press "somewhat as follows" that "I have a very serious communication to make to you today" (all the journalists begin taking notes).

Despite all of the handicaps, under the guidance of Józef Piłsudski, the chief of state, and Ignacy Jan Paderewski, the prime minister who represented Poland at the Paris Peace Conference, the Poles quickly organized an army that defeated the Bolsheviks, established a government of national unity, and in spite of all the domestic strife did not fall prey to a revolution contrary to Hungary.

Gibson and his three colleagues were supposed to give full assistance to the new Polish government as it strove to avert famine, revive its industry, reduce unemployment, appease ethnic tensions, define its borders, and put its ruined house in order.

Poland was populated by six different minorities, including 14% of Jews, and reports of pogroms, mostly in former Imperial Russian territory, were beginning to hit the front pages of American papers.

In June 1919, he and Dr. Boris D. Bogen,[14] general director of European relief operations of the American Jewish Joint Distribution Committee (JDC), and/or members of the Legation staff, traveled to several Polish cities (including Wilno, Lwów, Częstochowa, Kraków, and Pinsk), where such events had reportedly occurred.

[18] In Gibson's view, however, not all of these acts could be construed as anti-Semitic in intent since some had occurred on the volatile frontline of the Soviet-Polish War, and a number of Jews had rightly or wrongly been perceived as snipers or sympathizers of the Bolsheviks.

[20] Gibson believed that Polish anti-Semitism had largely been a product of the Imperial regimes, which "aroused and maintained public feeling against the Jews as part of the system of dominating through internal dissension."

That explained their presence in Paris during the Peace Conference and the fact that Felix Frankfurter (later Associate Justice of the US Supreme Court) wrote to Woodrow Wilson (May 22, 1919) that "the Polish Government must be bullied and browbeaten into quitting its policy of extermination and persecution.

"[25] A letter that Gibson wrote to his mother on 27 June 1919, three days after his meeting with Brandeis and Frankfurter, casts an interesting light on own his state of mind at the time: "I went down to the Relief Administration where I had two solid hours with Lewis Strauss [Herbert Hoover's private secretary] on the Jewish question.

I think that at the end of two hours I had convinced Lewis that I was not a Jew baiter and that I really want to help even if not in his simple way which consists chiefly in blackguarding the Polish Government for everything to be found in any report, no matter what its source, its foundation or its inspiration.

[26] Louis Marshall, President of the American Jewish Committee, was also present in Paris, also favored dealing sternly with the Polish government, and took the position that Gibson was willfully minimizing the whole matter to protect Poland.

He gathered more information than was possible by Gibson and his staff during their brief visits, but his conclusions did not satisfy the Zionist wing, which declared the report a "whitewash" of the Polish government and so the debate raged on.

He was also not fearful of the future of Polish-Jewish relations as he believed that the antagonism between the two communities was a legacy of the politics of the partitioning powers, Russia in particular, which would diminish when the country achieved a stage of normalcy."

His book includes the full text of a letter that Gibson sent to William Phillips, Assistant Secretary of State, on 6 July 1919, shortly after his meeting with Brandeis and Frankfurter in Paris.

He also evoked the "poisoned inheritance of the imperial powers," the last two of which had collapsed merely six months before Gibson himself set foot in Warsaw: "I did not realize just how far [the old Russian discrimination against the Jews] went until I came here.

It was about as cold blooded and fiendish as anything you can imagine... [for, by] barring the Jews from higher education, professions and the army, and keeping them out of 'Holy Russia' [it] forced them into all sorts of crooked work and disreputable means of getting a livelihood.

It was in those circumstances that he described the undesirable elements of the Foreign Service as "the boys with the white spats, the tea drinkers, the cookie pushers"[34] and suggested that they could be replaced by better men, who would be attracted by the more favorable conditions resulting from the passage of the bill.

Like many of his generation, he was acutely aware of the destabilizing effects of the Versailles Treaty and deeply concerned by the conduct of French diplomacy, which was animated by an understandable fear but unrealistically sought to ruin and humiliate Germany.

Reviewing the situation in 1942 (in The Problems of Lasting Peace, which was co-authored with Herbert Hoover) Gibson pronounced the whole course of French diplomacy in the 1920s and the 1930s, "except in certain intervals of Briand's ascendancy, incredible.

In Gibson's view, France's refusal to re-examine the ruinous load of reparation imposed upon Germany by the Versailles treaty, its initiative in forming an alliance of nations that totally encircled Germany, and its manifest footdragging in matters of disarmament set the stage for World War II by so weakening the democratic regime of German Chancellor Heinrich Brüning that it crumbled before the onslaught of the Nazis in 1933.

In his 1924 testimony before the House Committee on Foreign Affairs, he had compared his own situation to that of an admiral, sent on a trip around the world, "with instructions to call at various ports, entertain the right people and pay for all expenses, including provisions for his ship, out of his own salary.

After the outbreak of World War II, at the request of former Hoover, Gibson remained in Britain to negotiate authorization for the organization of food relief for the civilian population in territories occupied by German forces.

In March 1946, President Harry S. Truman[41] asked former Hoover to make an on-the-spot assessment of world food resources in order to avert a possible worldwide famine.