Having spent most of his career in the Foreign Office, he initially had some trouble adjusting to the role of ambassador, where he had far less control over the development of policy but in his time at Paris Bertie was able to play a substantial role in strengthening the Entente Cordiale between France and Britain into a genuine alliance, encouraging strong British backing for France during the Moroccan Crises of 1905 and 1911.

There are a large number of extant official letters marked "very confidential" that prove an intensive ongoing diplomacy on behalf of the Entente in the protracted period that preceded the First World War.

[12] As early as 1906 there were discussions about the possibility of a German invasion of France, yet always the proviso that it was in doubt, "that matters might be brought to a point in which a pacific issue would be difficult."

Bertie negotiated closely with Théophile Delcassé the foreign minister "toute occasion de concerter avec le Gouvernement Francais," warning them of the revulsion for war in France.

David Owen argues that this placed too great a reliance on the Admiralty and War Office to promise unequivocal support of a British Expeditionary Force.

One dispatch of April 1911 was so sensitive that it has since been destroyed by archivists: but it is clear that under Asquith, military leaders questioned Grey's competence; one of these critics was Bertie.

His military attache, Colonel Fairholme, clearly believed the French would outflank a German army on the frontier, which greatly exercised Bertie's mind "respecting strategical problems.

[16] However, the newly established Union of South Africa cried foul, as Delagoa Bay in Mozambique represented a strategic naval base area that could not be ceded to Germany.

In competing with the British Empire, Germany sought to acquire lands in southern Africa from Portugal, France, Belgium and Britain, in addition to promising the Portuguese government financial support.

After the February Revolution in Russia he advised the British government against the deposed Romanovs being allowed to go into exile in France as the ex-Empress Alexandra was perceived as pro-German.