What year was the Battle of Marignano, the defeat that turned Switzerland toward neutrality?

1515 → tail · tail.

At Marignano in 1515, French and Venetian forces crushed the Confederates. The shock ended Swiss expansion and set the country on its long path toward armed neutrality (while Swiss soldiers still served abroad as mercenaries). Peg 15 · 15 → tail · tail: two tails (an easy doubled image).