In 1417 the Confederates met in Lucerne to negotiate a compromise within the Confederation. They were successful in reaching a temporary compromise, but after Valais troops attacked and besieged Raron castles, Bern invaded over the Sanetsch Pass and plundered Sion in 1418. On 25 April 1419 both sides met in Zurich to attempt to reach an agreement. By 15 May of the same year when negotiations were going against the rebels, the Valaisan forces chose to leave the negotiating table and plundered a number of Bernese sheep on the way. In response Bern attempted another invasion across the Grimsel Pass with about 13,000 men. Bern was joined in the invasion by Fribourg, Solothurn, Neuchâtel and a few troops from Schwyz. Both Uri and Unterwalden refused to send troops to either side of the conflict.