There was no action near the White Sea–Baltic Canal during the Winter War of 1939-1940, when the USSR invaded Finland.
With Germany's full-scale invasion of the USSR in 1941, supported by Finland in the Continuation War, the canal route became the front line.

On June 23, 1941, the day after the German invasion, 16 Finnish commandos were ferried to the canal by two German Heinkel He 115 seaplanes from Oulujärvi.
The commandos were Finnish volunteers recruited by the German Major Schaller, and were equipped with German uniforms and weapons, as the Finnish General Staff wanted no responsibility for the operation.
The commandos were to blow up the canal locks, but they failed due to heightened security.

On June 28, the canal was bombed for the first time by the Finnish Air Force, targeting Locks No.
6, 7, 8, and 9, followed the next day by Finnish troops advancing along the Finland-USSR border.
The air bombings of the Povenets lock ladder succeeded in interrupting boat traffic on the canal only from June 28 to August 6, and then again from 13 to 24 August 1941.
On August 28, the fifth and final bombing raid of the 1941 navigation season took place against Lock No.
7, but it did no damage.

In August, the management of the BBK and most of the 800 canal staff were evacuated from Medvezhyegorsk to Lock No.
19 in Belomorsk, with only 80 left at their stations.

In November, a caravan of passenger vessels evacuating families of Povenets canal workers and residents, along with equipment, froze into the ice of Lake Vygozero.
On the night of November 12/13, another boat caravan froze in Zaonezhsky Bay near Megostrov Island, and was later captured by Finnish troops.
On December 5, Finnish troops entered Medvezhyegorsk.

On December 6 in a -37 °C frost, Finnish troops captured Povenets, the southern entrance to the BBK.

On the same day, Soviet troops started demolishing canal structures.
Lock No.
1 was the first to be blown up.

By the morning of December 8, Locks No 1 to 6, and dams No.
4 and 20 had all been demolished.

At the same time, heavy fighting took place near the Povenets Lock Ladder (Locks No.
1 to 7).
The Finns crossed the canal and captured Gabselga village to the east, but after a few days of fighting they were pushed back to the canal's western side.

Soviet sappers blew up Lock No.
7 on December 11 after the Red Army had retreated.
Once the locks of the Povenets Ladder had been destroyed, water from the watershed lakes poured freely into Lake Onega through Povenets village, which was nearly completely destroyed by the flood.
The route of the BBK had become the front line, separating the Finnish troops on the canal's western bank from the Soviet forces on its eastern bank.
The opposing armies held these positions until June 1944.
There was no action near the White Sea–Baltic Canal during the Winter War of 1939-1940, when the USSR invaded Finland. With Germany's full-scale invasion of the USSR in 1941, supported by Finland in the Continuation War, the canal route became the front line.
On June 23, 1941, the day after the German invasion, 16 Finnish commandos were ferried to the canal by two German Heinkel He 115 seaplanes from Oulujärvi. The commandos were Finnish volunteers recruited by the German Major Schaller, and were equipped with German uniforms and weapons, as the Finnish General Staff wanted no responsibility for the operation. The commandos were to blow up the canal locks, but they failed due to heightened security.
On June 28, the canal was bombed for the first time by the Finnish Air Force, targeting Locks No. 6, 7, 8, and 9, followed the next day by Finnish troops advancing along the Finland-USSR border. The air bombings of the Povenets lock ladder succeeded in interrupting boat traffic on the canal only from June 28 to August 6, and then again from 13 to 24 August 1941. On August 28, the fifth and final bombing raid of the 1941 navigation season took place against Lock No. 7, but it did no damage.
In August, the management of the BBK and most of the 800 canal staff were evacuated from Medvezhyegorsk to Lock No. 19 in Belomorsk, with only 80 left at their stations.
In November, a caravan of passenger vessels evacuating families of Povenets canal workers and residents, along with equipment, froze into the ice of Lake Vygozero. On the night of November 12/13, another boat caravan froze in Zaonezhsky Bay near Megostrov Island, and was later captured by Finnish troops. On December 5, Finnish troops entered Medvezhyegorsk.
On December 6 in a -37 °C frost, Finnish troops captured Povenets, the southern entrance to the BBK.
On the same day, Soviet troops started demolishing canal structures. Lock No. 1 was the first to be blown up.
By the morning of December 8, Locks No 1 to 6, and dams No. 4 and 20 had all been demolished.
At the same time, heavy fighting took place near the Povenets Lock Ladder (Locks No. 1 to 7). The Finns crossed the canal and captured Gabselga village to the east, but after a few days of fighting they were pushed back to the canal's western side.
Soviet sappers blew up Lock No. 7 on December 11 after the Red Army had retreated. Once the locks of the Povenets Ladder had been destroyed, water from the watershed lakes poured freely into Lake Onega through Povenets village, which was nearly completely destroyed by the flood. The route of the BBK had become the front line, separating the Finnish troops on the canal's western bank from the Soviet forces on its eastern bank. The opposing armies held these positions until June 1944.
White Sea–Baltic Canal