Mazeppa, being well aware that only warlike successes could secure his authority among the Cossacks, in 1689 attacked the Tatars of Oczakaf, and vanquished them in several engagements. The following year he accompanied the expedition of Galiczyn into the Crimea with his Cossacks, which ended in the discomfiture of the Tatars. Mazeppa was rewarded by rich presents and decorations. Soon after, by some means mentioned by several historians but never well explained, he attracted the eye of Peter the Great, by hinting to him a dark intrigue, secretly put in motion, by which his sister Sofia and her favourite Galiczyn were humbled for ever.
After the defection of Khmielnitski with his Cossacks from Poland to Russia, there were for a long time a certain part of the Polish Cossacks whose chiefs (attamans) were nominated by the kings of Poland. One of them, Paley, after defeating his rival Samuel, and exciting the jealousy of the Polish lords by his intrigues and wealth, passed over with numerous partisans to the Russians and acknowledged the supremacy of Mazeppa, who at that time was the sole chief or attaman of all the Cossacks, but that act of submission did not satisfy the daring adventurer. Paley was soon sent by his intrigues to Siberia, where he mained till the battle of Pultawa, and Mazeppa I obtained some advantages in several minor military-expeditions, which gratified the vanity of Peter the Great, who, in spite of the loss of 30,000 men, could not master the town of Azof at first. When, however, that crafty prince, obstinate in his views for the conquest of the Crimea, pressed that town with great vigour, Mazeppa, who got by accident secret intelligence in that town, requested his master to allow his Cossacks to storm it, which was accepted. The Cossacks, animated by the thirst of plunder and encouraged by the presence of their chief, had already climbed its walls, when its commander surrendered the fortress at discretion. Peter the Great, well aware of the importance of that town, which he attributed to Mazeppa's stratagem, did not fail to consider him as his best friend, and never failed to show him marks of his consideration; but as that prince had a sagacious eye, and was more than once frustrated in his views by the Cossacks, he ordered his generals to watch them closely, and did all he could to humble them, and, dividing them, quelled their insurrections by great atrocities.