23. If a Rook perpetually chases a Knight and the Knight only chases
back once, checks once, or has one check and one chase, the Rook side
has to change. (See examples in Diagram 49 and 50)

Diagram 49: Red (in Capital) moves first

R7-1 n2+1
R7-2 n1-2
R7+2 n2+1
R7-2 n1-2
R7+2 ....

Explanation:

The Black knight's "one chase one idle" does not violate the rule
but the Red Rook's perpetual chase does. Red has to change.

Diagram 50: Red (in Capital) moves first

R6+2 n2+3
R6-2 n3-2
R6+2 n2+3
R6-2 n3-2
R6+2 ....

Explanation:

The Black Knight is doing "one check one chase" which does not violate
the rule. The Red Rook is perpetually chasing the Black Knight. Red
has to change.