Von Vegesack chose his landing site with an experienced eye. The strait at Lemo offered natural protection for his fleet while giving access to the main road between Turku and Vyborg. If Swedish forces could sever that road and threaten Turku, they might force the Russians to negotiate. The general positioned his gunboats to command both the strait and the battlefield, creating an integrated defense that used sea power to compensate for his limited ground forces. Russian troops were scattered in small units along the main road, not expecting a major landing this far into their lines. The initial phases went exactly as planned. Swedish soldiers pushed inland through fields and forest, advancing several kilometers until the spires of Turku came into view. For a brief moment, it seemed the audacious plan might work.

The Libau Infantry Regiment arrived first to contest the Swedish advance. With a single gun, they launched a counterattack that pushed the forward Swedish units back to von Vegesack's main defensive line. The general responded with characteristic aggression, ordering an immediate assault on the Russian center. Russian commander Karl Gustav von Baggovut fed reinforcements into the fight: two companies on the right, two on the left, two with the gun in the center. It was Lieutenant von Vegesack, the general's own son, who spotted the opportunity. The Russian left flank hung exposed. The younger von Vegesack struck without hesitation. The Russians fell back several kilometers, and Swedish troops pursued, maintaining pressure as Sunday's long northern twilight faded into the white nights of Finnish summer.

Dawn on June 20 brought Russian reinforcements and renewed determination. Major General Nikolay Borozdin had assembled 300 men from the Brest Infantry Regiment, two additional guns, and a squadron of the Finland Dragoon Regiment. The Libau Infantry Regiment attacked before full light, driving the weary Swedes back to their defensive lines once again. Von Vegesack called in every man he could spare from the nearby islands, strengthening his positions while Baggovut prepared the decisive blow. When the Russian assault came, it came everywhere at once. The Pernov Musketeer Regiment attacked on the right. The Libau Regiment drove forward in the center. The Brest Regiment swept around the left. Russian artillery found the range on Ala-Lemo Manor house and set it ablaze, removing the Swedish command post in a column of smoke and fire.

With their defensive positions crumbling and the manor house burning, the Swedes had no choice but to fall back to the beach. The retreat could have become a massacre, but von Vegesack had prepared for this contingency. Shore fortifications covered the evacuation, and the gunboats that had blocked the strait now turned their guns on the pursuing Russians. Soldiers waded into the water, scrambling onto boats under artillery fire as Russian guns moved to the shoreline to engage the Swedish fleet directly. Von Vegesack managed to extract both his land and sea forces, pulling back to the relative safety of the Aland Islands. The Russian reserve forces at Yli-Lemo, two companies of the Nevski Regiment and half a squadron of Finland Dragoons, watched the Swedish sails disappear over the horizon. Finland's fate was sealed.

Two hundred years after the battle, sculptor Heidi Limnell created a monument called 'Kuoleva sotilas,' the Dying Soldier, and placed it near the Yli-Lemo Manor house. The work was inspired by 'The Tales of Ensign Stal,' Johan Ludvig Runeberg's epic poem cycle about the Finnish War that shaped how both Swedes and Finns remember this conflict. The Battle of Lemo never became as famous as the Finnish victories at Oravais or Lapua, perhaps because it ended in Swedish failure. But it captured something essential about the war: the desperate courage of men fighting for a cause already lost, the violence of close-quarters combat in peaceful farm country, the sound of artillery echoing across waters that had known fishing boats and trading vessels for centuries. Today, the battlefield lies quiet, the manor house rebuilt, the strait open to pleasure boats. Only the monument stands witness to the two days in June when Sweden made its last serious effort to hold Finland.