He was frustrated by French leaders such as Raymond Poincaré, who decided that Berlin was trying to weaken the Triple Entente of France, Russia and Britain and was not sincere in seeking peace.

[4] Cambon was nominated French ambassador at Washington, DC, in 1897 and in that capacity negotiated the preliminaries of peace on behalf of the Spanish government after the war against the United States.

Cambon believed in the Entente Cordiale with Britain and worked to reinforce and strengthen diplomatic ties with France's main ally.

His department shared military and other intelligence with the British Foreign Office in pursuit of the defeat of the Central Powers, Tsarism and Bolshevism.

[6][7] In 1928, he published what became a classic study of diplomacy, Le Diplomate, which was translated into English, Spanish, German, and Russian, and in it, he wrote, "What really distinguishes the diplomatist from the common herd is his apparent indifference to emotions; he is compelled to carry professional reserve to lengths which seem incomprehensible".