# Checkmate all the kings #4

Following the rules created by Lord of dark in this puzzle, and used here and here also, the idea is to find the minimum number of consecutive white moves to checkmate all the black kings (in this case 16). You cannot make a move that would put white in check.

Here's an interactive board.

RULES

• You are playing as White and you can make as many moves as you want before Black's turn.
• During your moves you can take any black piece except kings.
• During your moves your king can not be in check position.
• At the end of your turn all the black kings must be check mate : if Black can make one move that ends with one king being safe, you don't win. Note that this one move can't be a king moving to a threatened position.
• One piece can be used in multiple checkmates (you don't have to take all the king, just to checkmate them)
• Oh. My. Gooood. :-D – Rand al'Thor Mar 18 '17 at 17:16
• While these are all nice puzzles and I'm enjoying solving them, may I recommend that you not post too many all at once? There's a common effect on Puzzling where sequences of related puzzles end up with strictly decreasing scores. The first time people think "wow, this is cool", the second time "oh look, another one", the third time "meh, seen it already", the fourth time "oh God, not another one". This effect is even stronger when it's the same person posting them. – Rand al'Thor Mar 18 '17 at 17:20
• That certainly is the trend so far. – Dr Xorile Mar 19 '17 at 2:06

## 2 Answers

It can be done in 53:

This requires knights, obviously.

The kings on A1 and A8 can only be checked by knights on C2 and C7, which also check the kings on A3, A6, B4, B5.
The kings on A2, A4, A5, A7 can only be checked by knights as well, either:
- C1, C4, C5 and C8. This is a no-go, as it leaves B1 and B8 uncheckable except by two more knights, but with eight knights, there's no stopping one of the kings from taking one. They cannot defend themselves.
- C3 and C6, also checking B1 and B8.
Four more pieces needed to attack/defend B2, B3, B6, B7, C1-C8: four queens on C1, C8, E3, E6 can do that. Final position:

This can be done in

C7: three moves from G8.
C6: two moves from G8.
C3: three moves from G8.
C2: four moves from G8.
C1: two moves from H8.
C8: one move from H8.
E3: two moves from H8.
E6: two moves from H8.
G8: seventeen moves from G2-G5.
H8: seventeen moves from H2-H5.

Total: 53 moves.

B1, B4, B5, B8 were already covered by the knights.
B2, B7 are checked by the queens on C1 and C8.
B3, B6 are checked by the queens on E3 and E6.
C1, C3, C4, C5, C6, C8 are defended by the queens on E3 and E6.
C2 and C7 are defended by the queens on C1 and C8.

• In your final position, the kings at b2 and b7 aren't in check. Need moar knights! – Rand al'Thor Mar 18 '17 at 19:11
• @randal'thor More knights it is! – hvd Mar 18 '17 at 19:26
• But now the knights at c2 and c7 aren't defended. – Rand al'Thor Mar 18 '17 at 19:29
• @randal'thor Fewer knights it is! Seriously, I hope I didn't miss anything now, I went over the complete B and C columns as a sanity check. – hvd Mar 18 '17 at 19:42
• That seems to work. I haven't checked all your move counts, but who cares - have a +1 anyway. – Rand al'Thor Mar 18 '17 at 19:44

I see a tiny bit faster way, 52 moves.

 Horses on C2-C7, queen on D6, king on D3.
29 moves for promotions.
23 moves for horses, queen and king.
C7: 3 from G8.
C6: 2 from G8.
C5: 3 from G8.
C3: 3 from G8.
And C4: 3 from H8.
C2: 5 from H8.
D6: 2 from H8.
D3: 2 moves.


• Does this checkmate the kings on B1/2/7/8? Can they not move to C1/8, or am I visualising this wrong? – hvd Apr 21 '17 at 15:41
• Yeah, you are right, they are only in check. Forgot about that. Damn. – Zizy Archer Apr 24 '17 at 7:33