Reference

The card game Kaschlan appears to share similarities with the Russian card game Durak. In Durak, the rules to determine how a new attacker is chosen are as follows:

1. Winning the Attack: If the current defender cannot beat the attack with a higher card or a trump card, they must pick up all the cards that were used in the attack. In this case, the same attacker continues to be the attacker in the next round.
2. Defeating the Attack: If the defender successfully beats off the attack by using higher cards or trump cards, they become the new attacker. The player on their left then becomes the new defender.

For more detailed rules on Durak, you can refer to sources such as the Wikipedia page on Durak here.

If Kaschlan's rules are slightly different, it might be necessary to look up specific rules of this game, but often traditional card games share these common principles for switching roles between players.