The Russian vanguard made contact with the Swedish rearguard at Sangis, however the fighting ended abruptly and the two sides parleyed. Gripenberg, who found his situation hopeless with the Russians moving on his flank, received a letter from Cronstedt, in which the retreating general overestimated the Russian force to 10,000–11,000 men; for this reason, as he incorrectly believed he would be cut-off from southern Sweden by a large Russian force,[note 1] and as the Swedes were promised to be dismissed rather than kept as prisoners (on the condition that they withdrew from the war), he capitulated on March 25—in what would be known as the Convention of Säivis. Gripenberg's force was mostly made up of battle-hardened Finns who, as they marched through Tornio, surrendered their weapons at Kemi Church and wandered home, to Finland. The capitulation involved a total of about 7,075 men and all their provisions,[note 2] a number in which sick and non-combatants are included as well as troops not present at Kalix; as was the case with the Swedish Västerbotten Regiment, of which one battalion refused the capitulation terms and was instead captured at the Battle of Skellefteå.
At the time, the capitulation was deemed as an act of treachery—comparable to Carl Olof Cronstedt's surrender at Sveaborg—however, under the prevailing circumstances and with the information granted to him, the court-martialed Gripenberg was not solely to blame. The Russian threefold attack had nevertheless failed to achieve a quick desirable peace, for which reason Knorring lost his supreme command to Barclay. The war, which meant the end of Swedish rule over Finland, would continue until 17 September 1809.