In 1353 Bern joined the Swiss Confederacy, becoming one of the eight cantons of the formative period of 1353 to 1481. Bern invaded and conquered Aargau in 1415 and Vaud in 1536, as well as other smaller territories; thereby becoming the largest city-state north of the Alps, by the 18th century comprising most of what is today the canton of Bern and the canton of Vaud.
What year did Bern invade Aargau?
1415