Düna
Kokenhausen was one of three major forts blocking the Swedish progress on the line of the Daugava River. Swedish forces of about 2,000 under Carl Carlsson Gyllenhielm had been blockading the fortified town of Kokenhausen, located on Daugava River, between Riga and Daugavpils - since 10 March - after the arrival of Duke Charles with heavy artillery - laying a siege to it since 28 March. On 1 April the Swedes had taken the town but not the inner castle, which was still defended by a Polish-Lithuanian garrison. Charles left about 2,600 strong besieging force, and moved north to Erlaa.