If you’ve played even a few games of shogi, you’ve probably heard someone say “nifu!” in a slightly panicked voice.
Maybe it happened to you. You’re feeling clever. You have a pawn in hand. You see a good square. You drop it… and then the game ends right there because it’s illegal.
That’s rough. So today I want to talk about the nifu rule, including what it is, why it matters, and the coolest part: how far back we can trace it in shogi history using Japanese sources.
And yes, we’ll also look at a few “pawn-related” rules that are basically nifu’s cousins.
First: what is “nifu” in plain English?
“Nifu” (二歩) literally means “two pawns.”
In modern shogi rules, you cannot drop a pawn onto a file (a vertical column, called a suji in Japanese) if you already have an unpromoted pawn somewhere on that same file.
A couple of important details:
- This is only about pawns you own, not your opponent’s pawns.
- This is only about dropping a pawn from your hand (打つ / utsu). You can still move your pawn forward normally.
- A promoted pawn (tokin, と) does not count as a pawn for this rule. So if your pawn has promoted on that file, dropping a new pawn on that same file is allowed.
In official play, nifu is a foul that loses immediately. That means, no warnings, no “oops, take it back.” It’s right there in the official match rules as one of the instant-loss violations.
Nifu only makes sense because shogi has drops
Here’s the big idea that makes shogi feel like shogi:
When you capture a piece, it doesn’t disappear forever. You keep it in your hand, and later you can drop it back on the board as your own piece.
That rule (持ち駒 / mochigoma) is one of shogi’s most famous features, and the Japan Shogi Association describes it as a major turning point in the game’s history. Their historical overview says that around the time modern-style shogi formed (often described as the 15th–16th century), the rule of reusing captured pieces began.
Drops are fun because they create comebacks and wild tactics. But drops also create problems. And pawns are the biggest “problem child” because:
- There are a lot of pawns.
- Pawns are easy to capture.
- A pawn dropped in the right spot can change everything.
So shogi needed “guardrails.” Nifu is one of those guardrails.
A 1636 shogi book gives us a huge clue
Now for the history part.
One of the most famous early sources is a shogi problem collection from 1636 called 『象戯圖式（象戯図式）』(Shogi diagram), often known by its nickname 『将棋智実』(Shogi Wisdom).
You can find this title listed in Japan’s 国書データベース (Kokusho Database) with the publication year given as 寛永13年 (1636). Waseda University’s classical book collection also catalogs it with the same year, and even lists names connected to the book (including 林羅山 / Hayashi Razan in the front matter).
Why do shogi puzzle collections matter for rules? Because serious puzzle books don’t just show tactics. They show what the writer assumes is legal.
And the Japanese Wikipedia article on nifu points out something really fun:
- The first tsume-shogi (mate problem) built around nifu as a main theme was made by 二代大橋宗古 (the second Ōhashi Sōko), and it appears as Problem #1 in 『象戯図式』 (1636).
So by 1636, nifu wasn’t some random local habit. It was important enough to be part of high-level puzzle writing.
Even more interesting: that same article notes that the “no nifu” idea shows up even earlier in tsume-shogi. It gives an example from 『象戯造物』 (1602) (The Origins of Shogi) (linked to 初代大橋宗桂, The First Ōhashi Sōkei), where the defending side could avoid mate if they were allowed to use a nifu-style blocking pawn—meaning the composer already treated nifu as illegal.
That doesn’t 100% prove every casual player in 1602 followed the rule in regular games… but it’s a strong clue that the concept was already known.
So why ban nifu at all?
Here’s the honest answer: we can’t time-travel and ask the rule-makers. A lot of the “why” is educated guesswork.
But Japanese writing on the topic often circles around the same idea:
If nifu were allowed, pawns would become too powerful, and many positions would become too one-sided or repetitive.
Think about what a pawn does in shogi:
- It claims space.
- It opens lines for rooks and bishops.
- It forces responses because it threatens to promote.
- It can act like a “plug” that blocks an attack.
Now imagine being allowed to stack pawns in one file by dropping them over and over. You could build a pawn wall on defense, or you could smash forward with extra pawn pushes on offense. Either way, pawns start to crowd out the rest of the game.
Also, pawns are cheap and common. If the cheapest piece can be stacked freely, the whole balance shifts.
So nifu is basically shogi saying, “Yes, drops are awesome. But pawns need a safety lock.”
Nifu’s “related rules”: the other pawn guardrails
Nifu didn’t grow up alone. In the official rules list of instant-loss fouls, it sits next to a few rules that feel like they’re part of the same family:
1) Pawn-drop mate is illegal
This is the famous rule: 打ち歩詰め (uchi-fuzume).
It means you cannot drop a pawn that gives checkmate right away, when the opponent has no legal way out.
Even many strong players have to pause and double-check this one, because “pawn drop check” is often a good move… but “pawn drop checkmate” is not allowed.
This rule is so tied to pawn drops that it gets taught right next to nifu in beginner materials.
2) You can’t drop a piece where it has no moves
This one has a long Japanese name: 行き所のなき駒の禁.
In simple terms: you can’t make a move that leaves your piece with zero legal moves.
Common examples:
- Dropping a pawn (or lance) on the last rank.
- Dropping a knight on the last two ranks.
- Moving a pawn to the last rank without promoting (because then it couldn’t move).
This rule matters because drops let you place pieces anywhere. Without this rule, you could “dump” useless pieces in weird places just to waste time or block squares.
3) Repetition rules (and the “perpetual check” loss)
Modern shogi also has rules about 千日手 (sennichite)—repeating the same position.
In today’s official rules, repetition is generally treated as a draw situation that leads to a replay, but there’s a special case:
If one side repeats the position by giving check every time, that becomes 連続王手の千日手, and the player who kept giving the checks loses.
That’s another guardrail. It’s the game saying, “You can’t force a draw just by checking forever.”
And historically, Japanese shogi writing about early rule lists connected to 『象戯図式』 often mentions repetition handling alongside nifu and pawn-drop rules—showing that these issues were already on people’s minds when they were trying to standardize the game.
What to take away from all this
When you look at nifu with fresh eyes, it stops feeling like an annoying “gotcha.”
It becomes something else:
Nifu is one of the rules that makes shogi’s drop system work.
It protects the game from turning into “pawn stacking simulator.” It keeps openings and defenses from becoming too simple. And it forces us to treat pawns with respect—because you can’t just spam them down the board.
So the next time you’re about to drop a pawn, do the classic nifu check:
- Look up and down that file.
- Make sure you don’t already have an unpromoted pawn there.
- If you do… maybe it’s time to aim for a trade, a push, or a promotion first.
Your future self (and your rating) will thank you.