All navies of the sailing era kept a number of gunboats on hand. Gunboats saw extensive use in the Baltic Sea during the late 18th century as they were well-suited for the extensive coastal skerries and archipelagoes of Sweden, Finland and Russia. The rivalry between Sweden and Russia, in particular, led to an intense expansion of gunboat fleets and the development of new gunboat types. The two countries clashed during the Russo-Swedish war of 1788–90, a conflict that culminated in the massive Battle of Svensksund in 1790, in which over 30,000 men and hundreds of gunboats, galleys and other oared craft took part. The majority of these were vessels developed from the 1770s and onwards by the naval architect Fredrik Henrik af Chapman for the Swedish archipelago fleet. The designs, copied and refined by the rival Danish and Russian navies, spread to the Mediterranean and to the Black Sea.