Who is faster.

Tempo, not material

Because captured pieces come back as drops, an attacker never runs out of ammunition and a defender never runs out of walls. So the endgame is not decided by who has more; it is decided by who gets there first. A player a rook down who mates one move earlier has not won “despite” the rook. The rook was irrelevant.

The unit of that race is the threatmate, 詰めろ: a position where the attacker mates next move if left alone. Everything below counts in threatmates.

The count

A side’s count is the number of free moves it needs to deliver mate, assuming the opponent does nothing but pass. Japanese writes the count as N手すき, “N moves of slack.”

• Mate available now: count 0. Play it.
• Threatmate 一手すき: count 1. One more free move and the king is mated.
• Two moves from a threatmate 二手すき: count 2. One preparing move, then the threatmate, then the mate.
• And so on. Past three the count stops being useful and the middlegame has not ended yet.

The procedure, on every move of the endgame:

1. Their count against my king. If it is 0, I am mated whatever I do, unless I can mate first. If it is 1, I must answer the threat this move, unless I can mate first.
2. My count against their king. If it is 0, mate. If it is 1, I have a threatmate available.
3. Compare, and remember whose move it is. It is my move. If my count is less than or equal to theirs, I attack: I get there first. If my count is greater, I defend, and I look hardest for the defence that also lowers my count.

The whole of endgame judgement is those three lines, applied honestly. The hard part is not the arithmetic; it is counting your opponent’s attack as generously as your own.

One position, both counts

Black to move. Both dragons are two moves from a mate, both sides hold a gold, and the engine has counted both sides.

• Black’s count is 2. No mate exists now (the engine checked every move), and ▲+R-5b threatens ▲G*3b next.
• White’s count is 2. If White had the move, no mate exists; one preparing move, △+R-4h, and △G*7h would be mate.
• Black is to move. 2 is not greater than 2, so Black attacks. The dragon goes to 5b.

The race, played out

White’s correct reply was to defend: the engine finds exactly four true parries to ▲+R-5b, △G*2b, △G*3b, △G*4b, △+R-4b. Each one spends the gold or the dragon that White’s attack needed, so White’s own count rises, and Black keeps the initiative.

The threatmate that escapes a threatmate

The best defensive move in shogi is a parry that is itself a threatmate: tsumero-nogare no tsumero, 詰めろ逃れの詰めろ. It answers the opponent’s count and lowers your own in the same move, which is worth two tempi, and it is the move strong players look for first when they are behind in the race. None of White’s four parries above does that; each defends and nothing more.

Its opposite is the spite check: a check that gains nothing. In the position above White can throw the gold in with check, △G*7h, and Black simply takes it.

After △G*7h ▲Kx7h Black’s threatmate stands exactly as before, and White has lost the gold that made White’s own count 2. The engine confirms the mate threat is still there. A check that does not change the count is a free move for the other side.

Three ways to lose the count

• Checking for its own sake. The proverb says ōte wa oitte: a check is a chasing move. Unless it takes a square away or brings a piece closer, it hands the tempo back.
• Defending when you are faster. If your count is lower and your king is not in a threatmate, a defensive move is a wasted move, and the opponent’s count falls by one while yours stays.
• Not recounting. Every capture changes both hands, and both counts with them. The count you did three moves ago is a count of a different position.