Immediately after the accession of Nicholas to the throne, war broke out with Persia.  It was of short duration.  The Persian monarch, utterly discomfited, was compelled to cede to Russia large provinces in the Caucasus, and extensive territory on the south-western shore of the Caspian, and to pay all the expenses of the war.  Immediately after this, on the 7th of May, 1828, war was declared against Turkey.  The Russian army, one hundred and sixty thousand strong, flushed with victory, crossed the Pruth and took possession of the entire left bank of the Danube, for some hundreds of miles from its mouth, with all its fertile fields and populous cities.  They then crossed the river, and overran the whole region of Bulgaria.  The storms of winter, however, compelled a retreat, which the Russians effected after most terrific conflicts, and, recrossing the Danube, they established themselves in winter quarters on its left banks, having lost in the campaign one half of their number.  The Turks took possession of the right bank, and remained, during the winter, in face of their foes.  In the spring of 1829 the Russians, having obtained a reinforcement of seventy thousand men, opened the campaign anew upon the land, while a fleet of forty-two vessels, carrying fifteen hundred guns, cooeperated on the Black Sea.

Through fields of blood, where the Turks, with the energies of despair, contested every step, the victorious Russians advanced nearly three hundred miles.  They entered the defiles of the Balkan mountains, and forced the passage.  Concentrating their strength at the base of the southern declivities, the path was open before them to Constantinople.  Pushing rapidly forward, they entered Adrianople in triumph.  They were now within one hundred and fifty miles of Constantinople.  The consternation in the Turkish capital was indescribable, and all Europe was looking for the issue with wonder.  The advance guard of the Russian army was already within eighty miles of the imperial city when the sultan, Mahmoud IV., implored peace, and assented to the terms his victor extorted.

By this treaty, called the treaty of Adrianople, Turkey paid Russia twenty-nine millions of dollars to defray the expenses of the war, opened the Dardanelles to the free navigation of all Russian merchant ships, and engaged not to maintain any fortified posts on the north of the Danube.

In July, 1830, the Poles rose in a general insurrection, endeavoring to shake off the Russian yoke.  With hurricane fury the armies of Nicholas swept the ill-fated territory, and Poland fell to rise no more.  The vengeance of the tzar was awful.  For some time the roads to Siberia were thronged with noble men driven into exile.

In the year 1833, Constantinople was imperiled by the armies of Mohammed Ali, the energetic pacha of Egypt.  The sultan implored aid of Russia.  Nicholas sent an army and a fleet, and drove Mohammed Ali back to Egypt.  As compensation for this essential aid, the sultan entered into a treaty, by which both powers were bound to afford succor in case either was attacked, and Turkey also agreed to close the Dardanelles against any power with whom Russia might be at war.