Just before he was officially appointed foreign minister, Sazonov attended a meeting between Nicholas II of Russia and Wilhelm II of Germany in Potsdam on 4-6 November 1910. This move was intended to chastise the British for their perceived betrayal of Russia's interests during the Bosnian crisis. Indeed, Britain's Foreign Secretary was seriously alarmed by this token of a "German - Russian Détente".

The two monarchs discussed the ambitious German project of the Baghdad Railway, widely expected to give Berlin considerable geopolitical clout in the Fertile Crescent. Against the background of the Persian Constitutional Revolution, Russia was anxious to control the prospective Khanaqin - Tehran branch of the railway. The two powers settled their differences in the Potsdam Agreement, signed on 19 August 1911 and giving Russia a free hand in Northern Iran. As Sazonov hoped, the first railway connecting Persia to Europe would provide Russia with a lever of influence over its southern neighbour.

Notwithstanding the promising beginning, the Russian - German relations disintegrated in 1913, when the Kaiser sent one of his generals to reorganize the Turkish army and to supervise the garrison in Constantinople, remarking that "the German flag will soon fly over the fortifications of the Bosphorus", a vital trade artery which accounted for two fifths of Russia's exports.

Despite his fixation on Russian - German affairs, Sazonov was also mindful of Russian interests in the Far East. In the wake of the disastrous Russo - Japanese War, he steadily made friendly overtures toward Japan. As a result, a secret convention was signed in St. Petersburg on 8 July 1912 concerning the delimitation of spheres of interest in Inner Mongolia. Both powers determined to keep Inner Mongolia politically separate from Outer Mongolia. Four years later, Sazonov congratulated himself on concluding a Russian - Japanese defensive alliance (3 July 1916) aimed at securing the interests of both powers in China.

In the run-up to a major military conflict in Europe, another concern of the Russian minister was to isolate Austria - Hungary, mainly by playing the Balkan card against the dwindling power of the Habsburgs. Since Sazonov was moderate in his Balkan politics, his ministry "came under frequent nationalist fire for failing to conform to a rigid pan-Slav line".

While the extremist agents like Nicholas Hartwig aspired to solidify the conflicting South Slavic states into a confederacy under the aegis of the Tsar, there is no indication that Sazonov personally shared or encouraged these views. Regardless, both Austria and Germany were persuaded that Russia fomented Pan - Slavism in Belgrade and other Slavic capitals, a belligerent attitude in some measure responsible for the Assassination in Sarajevo and the outbreak of the Great War.

As the World War unwound, Sazonov worked to prevent Romania from joining the Central Powers and wrested in March 1915 an acquiescence from Russia's allies to the post - war occupation of the Bosphorus, Constantinople, and the European side of the Dardanelles. On 1 October 1914 Sazonov gave a written guarantee to Romania that, if the country sided with the Entente, it would be enlarged at the expense of the Austrian dominions in Transylvania, Bukovina, and the Banat. In general, "his calm and courteous manner did much to maintain fruitful Allied relations".

Sazonov was viewed favourably in London, but the Germanophile faction of Tsarina Alexandra fiercely urged his dismissal, which did materialize only after the minister had aired a proposal to grant autonomy to Poland.

Early in 1917, Sazonov was appointed ambassador in Great Britain, but found it necessary to remain in Russia, where he witnessed the February Revolution. He was opposed to Bolshevism, advised Anton Denikin on international affairs, and was foreign minister in the anti - Bolshevik government of Admiral Kolchak. In 1919 he represented the White movement at the Paris Peace Conference. Sazonov spent his last years in France writing a book of memoirs. He died in Nice where he is buried.