The opposing fleets met on 29 June-the Russian fleet armed with 552 cannon and the Turks, with 1,120. For three days they maneuvered in sight of each other, gradually heading toward the estuary of the Danube and farther away from Ochakov. At last, on 3 July near Thedonisi Island, the Kapudan Pasha ordered his fleet to engage the Russians. An experienced commander, Hassan Pasha knew the weak points of the Russian fleet and directed his main offensive, six ships of the line, at the Russian vanguard, containing the 40-gun frigates Berislav and Strela [Arrow]. The frigates held out under the heavy fire but Voynovich, intimidated by the massive Turkish forces, did not assist his vanguard. A critical moment developed because the Turkish forces were now in a position to disrupt the line of the Russian fleet, a ma-neuvre which would inevitably defeat a Russian squadron.
The Turks were about to send word of their victory to the sultan when vanguard commander Commodore Fyodor Ushakov began a counterattack. From the bow of the Saint Paul Ushakov opened fire on Hassan's vessel. The maneuvre was a success. Not only was the Turkish flagship disabled, but four warships were badly damaged. Led by the Kapudan Pasha, the entire Turkish fleet retreated. Owing to the skill and bravery of Ushakov, the Russian fleet succeeded in winning the victory of Thedonisi and distracting the enemy from Ochakov for nearly a week. Though Voynovich abandoned an attempt to chase the Kapudan Pasha, and the latter returned to the firth, the Turkish seamen were unable to defend the fortress at Ochakov. On 6 December 1788, the Russian army took Ochakov by storm. In his report on the victory Admiral Voynovich attempted to give less credit to Ushakov. Prince Potemkin resolved the resulting hostility between the two officers, promoting Ushakov in early 1789 to commander of the Sevastopol squadron. After further heroism Commodore Ushakov would be promoted to the rank of Rear Admiral.
In reality, the successes of the Russian army very often depended upon the assistance of the fleet. The naval forces, for example, waged an unceasing campaign against Turkish transport ships-the Turks' chief means for supplying their land forces. Among the most damaging attacks upon the Turkish supply ships was made by the young Lieutenant-Commander Dmitry Senyavin. With a small squadron of four vessels, Senyavin destroyed nine enemy transport ships and took two captive. In the campaign of 1789 both the Turks and the Russians avoided decisive battles. Russian seamen made good use of the year; they combined Ushakov's forces, the firth squadron, and reinforcements from Taganrog, and stationed them all at Sevastopol.
In the spring of the next year Rear Admiral Ushakov, aboard the Alexander Nevsky, rounded the eastern coast of the Black Sea accompanied by a small squadron. During the campaign Russia managed to destroy or capture fifteen Turkish merchant vessels as well as shell the fortresses of Samsun and Anapa.
Meanwhile, the Turkish fleet came under the command of a new Kapudan Pasha, Hussein, who dreamt of nothing but Turkish victory. The Sultan had great confidence in him, and in late June the ambitious Kapudan Pasha appeared near the Crimean coast, bound for Kerch. Ushakov and his fleet set out in search of enemy vessels, and the battle grew nearer. The fleets met on 8 July 1790 off the Kerch Strait. The Turks had ten ships of the line and eight frigates. Admiral Ushakov, accustomed to being outnumbered, could advance only sixteen lower-rated ships and frigates. The Turks also outnumbered the Russians in weaponry, 1,100 cannon to 836.
Sailing with a favourable wind, Hussein was the first to launch an attack. Turkish vessels quickly approached the Russian vanguard. At that time Ushakov deliberately led six weak frigates out of his attack line, forming them into a reserve corps. The rest of the vessels closed in, and the battle line of the Russian force was then able to withstand that of the Turks.
The cannonade continued for three hours. The ships drew closer and closer together. True to form, Ushakov, on board his 80-gun ship Rozhdestvo Khristovo [Christmas], attacked Hussein's flagship. Hussein could not withstand the assault and withdrew. In an hour the rest of the Turkish ships followed the Kapudan Pasha in a disorderly retreat. Ushakov himself led the chase after the retreating Turks, and it was only the approaching darkness that ended the chase and prevented Hussein's capture. The Turks narrowly avoided utter defeat, while moonlight illuminated the remnants of the battle: Russia's Black Sea Fleet lost 97 men, sank one Turkish cruiser and seriously damaged several other vessels. Despite his own determination and the confidence of his sultan, Hussein had failed to reach the Crimean coast.