In 1696, at the mouth of the river Don, a Russian flotilla of armed rowboats blocked the supply of the Ottoman fortress of Azov. On the 1700 engraving by Adrian Shkhonebek, "Taking the fortress of Azov. 1696", depicts the ships carrying rectangular panels on the flagpoles, the heraldic shading of which shows that some of the flags are blue with a straight red cross, and the rest are white with a straight red cross. A number of researchers doubt the accuracy of Shkonebek's engraving because he was not a witness to the events.