16. One cannon perpetually chases two rooks can be ruled a draw; two cannons perpetually chase two rooks can also be ruled a draw. (See examples in Diagram 26, 27, and 28.)

Diagram 26: Red moves first

C2=1 r9=8
C1=9 r1=2
C9=2 r8=9
C2=8 r2=1
C8=1 ...

Explanation:
Red's cannon keeps attacking the two Black rooks alternately. This is allowed and the game can be ruled a draw.

Diagram 27: Red moves first

C4+1 r2+2
C4+3 r4+3
C4-5 r2-5
C4+2 r4+2
C4+3 ....

Explanation:
Red's cannon keeps attacking the two Black rooks alternately. This is allowed and the game can be ruled a draw.

Diagram 28: Red moves first

C4+1 r2-3
C2-1 r4-4
C4+2 r4+2
C2+2 r4+2
C2+3 r2+3
C4-4 r4-4
C2-3 r2-3
C4+4 r4+4
C2+3 ....

Explanation:

Two Red cannons altenately chase two Black rooks. This is different than two pieces perpetually chase one piece or one piece perpetually cahses one piece and is allowed. This game is a draw.