Answer
Barclay led troops 100 km across the Gulf of Bothnia, a daring feat that took place during the Russo-Swedish War of 1808-1809. The crossing was made on ice, and Barclay's troops faced treacherous conditions and the threat of enemy attack. Despite the challenges, Barclay's leadership and the resilience of his troops ensured the successful completion of the crossing, which played a significant role in the Swedish victory in the war.