The scope of corsair activity began to diminish in the latter part of the 17th century, as the more powerful European navies started to compel the Barbary States to make peace and cease attacking their shipping. However, the ships and coasts of Christian states without such effective protection continued to suffer until the early 19th century. Between 1801 and 1815, occasional incidents occurred, including two Barbary wars waged by the United States, Sweden and the Kingdom of Sicily against the Barbary States. Following the Napoleonic Wars and the Congress of Vienna in 1814–15, European powers agreed upon the need to suppress the Barbary corsairs entirely. The threat was finally subdued by the French conquest of Algeria in 1830 and subsequent pacification by the French during the mid-to-late 19th Century.