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油断大敵 yudan taiteki Carelessness is one's greatest enemy

油断大敵 (yudan taiteki), carelessness is a great enemy, is a Japanese proverb. Its older form is cited as a common saying in the 甲陽軍鑑, a military chronicle compiled by 1621. This study follows it to a Confucian scholar's chapter of 1732 and into English, and sets out the two stories told for 油断.

Japanese Scroll of Carelessness is one's greatest enemy (yudantaiteki) — Calligraphy by Eri Takase
Carelessness is one's greatest enemy油断大敵yudan taiteki

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Abstract

油断大敵, carelessness is a great enemy, is a Japanese proverb. Its older form, 油斷强敵, carelessness is a strong enemy, is already cited as a common saying in the 甲陽軍鑑, a military chronicle compiled by 1621; the 毛吹草 of 1638 lists it with a verb, and the form with 大 is in a puppet play of 1668. Muro Kyūsō 室鳩巣, in 1732, built a whole chapter of his 駿台雑話 on it, telling how the elder statesman Ii Naotaka 井伊直孝 gave it as his one-phrase transmission to a rising young minister, and setting it, a rustic proverb, beside a Zhou king's own maxim, the Red Book's four lines on care and negligence. The word 油断 itself has no settled origin: one dictionary prints two stories, a sutra's spilled oil and a worn-down native word, and the other marks it unknown.

Overview

The sense. The sense has not moved: a warning against the relaxed guard. What the witnesses add is a scale. In the military chronicle it is a camp that posted no watch; in the puppet play it is a commander's regret after an ambush; in Kyūsō it is the whole of a statesman's counsel, dignified by a Zhou king's maxim; on the children's card it is a house on fire; in the modern dictionaries it is the everyday word for don't get complacent. The one variant, 油断強敵, carelessness is a strong enemy, is older than the form with 大: the chronicle writes it as four characters, the 毛吹草 with a verb, becomes a strong enemy, and the dictionaries list it as a synonym. Kyūsō's reading is the hard one, and the 1894 editor made it a title: no other enemy counts.

The words. 油断, yudan, is the moment of a dropped guard: 気をゆるすこと、たかをくくって注意をおこたること, letting the mind relax, underrating a thing and neglecting attention. It is not habitual sloppiness, which is why carelessness, unpreparedness and complacency are each about as near as the other. The word is Japanese and its origin is not known; the 精選版日本国語大辞典 marks it 語源未詳 and dates it from a 1309 manuscript of the Tale of the Heike, where it appears once, in the form ゆたむ. Of the other recensions of the same passage, the 長門本 has the word and the 屋代本 and the 源平盛衰記 use other words, and the dictionary finds it nowhere else in that manuscript, nor in the 保元, the 平治 or the 覚一本 Heike, so it was not yet common in the fourteenth century [1]. Two stories are told about where it comes from, and デジタル大辞泉's note prints both, the first as it is said, the second as one theory. One is a sutra, the 北本涅槃経, chapter 22, where a king orders a courtier to carry a bowl of oil through a crowd: 若棄一渧、當斷汝命, if you spill one drop, your life shall be cut off. The story joins 油, oil, to 断, cut off. The other is a native word, ゆたに, at ease, slack, worn down by sound change. Neither is more than a theory. 大敵, taiteki, is a great enemy, a formidable foe, and the proverb is a predicate: carelessness is a great enemy. 断 is written 斷 in the typeset books before 1946, and the Edo prints write the word in a running hand; the modern form is the one now used.

The proverb in English. It has been in English since James Curtis Hepburn's dictionary of 1867, as negligence is a great enemy [2], the form Hepburn's later editions and the Meiji language primers kept. Carelessness is a great enemy is in print by 1889, in a London commentary on the Book of Proverbs [3], and carelessness is the greatest enemy, the house title's nearest ancestor, in Gordon Prange's account of Pearl Harbor in 1963 [4]. The proverb is not in Galef's, Zona's or Trimnell's paperbacks.

The historical record

By 1621, printed 1656. 甲陽軍鑑, the military chronicle of the Takeda house, chapter 23. The chronicle is ascribed to Kōsaka Masanobu 高坂昌信, compiled by Obata Kagenori 小幡景憲 before 1621, and first printed in 1656 [5]. Of the Murakami commanders facing the young Takeda Harunobu, it says that they judged the enemy general green, and then: 少人數といひ旁以て油斷强敵といふことを忘れ味方よりはり番をも一人出さず, his force being small too, for all these reasons they forgot the saying carelessness is a strong enemy and sent out not one man of their own to keep watch. The saying is cited as one everybody knew, and the lapse it names is a camp's [6].

1638, printed 1645. 毛吹草, by Matsue Shigeyori 松江重頼, the earliest collection of proverbs of the Edo period. The book's list of sayings, 世話付古語, has ゆだん强敵となる, carelessness becomes a strong enemy, a line after 猫の額なる物を鼠がねらふ, the mouse eyes what is on the cat's forehead, as Fujii's 1929 reproduction of the list prints it and the 1943 edition reads; the 1910 dictionary gives it as 【油斷、强敵トナル】 [7][8]. A verse later in the same book already uses the four characters without the verb: とく見ぬや油斷强敵花の風, hurry and look: carelessness is a strong enemy, the wind in the blossoms [8].

1660. わらんべ草, a treatise on kyōgen by Ōkura Toraaki 大蔵虎明. かならずめやすき所にけがあり。油断がうてきなり, the slip always comes where it looks easy: carelessness is a strong enemy. The 精選版日本国語大辞典's first example of 油断強敵 in a dated work, read ごうてき [9].

1668. The puppet play 源平敵討遺恨并頼光北国, act four. なむ三ぼう、かやうにないがまへを、してをきたりしを、しらずして、ゆだんたいてきとなしたる事の口をしやと, Buddha help us: not to have known they had made ready like this, and to have let carelessness be our great enemy, how bitter. This is the line the 精選版日本国語大辞典 gives as the first attestation of the form with 大, still with となす, to make into [10].

1718. やふにまくは, a joke-book. 六月夜に釜ぬかるゝ油断強敵猫の額の飯粒ねらふ鼠あり, the kettle stolen on a June night: carelessness is a strong enemy; there is a mouse that eyes the grain of rice on a cat's forehead. The older form, still alive fifty years after the form with 大, and set beside the mouse and the cat's forehead that stand a line apart from it in the 毛吹草's list [11].

1732, printed 1750. Muro Kyūsō, 駿台雑話, book four. The Confucian scholar builds a chapter on the proverb, and heads it with the four characters and their reading, ゆだんたいてき. In the Kan'ei years Nagai Naomasa 永井尚政, young and rising fast in the shogun's favor, met the old Ii Naotaka, the elder statesman of the age, and asked him for anything from his long experience that a young man in high office should keep. Naotaka said he had one thing, too important to say in passing, and named a day; Nagai came in formal dress to his house, and after the greetings Naotaka said: 世話に油断大敵といふ事定て御覚へあるべし、某が伝授外にはなく候、此一言にて候ぞ、必御忘れあるな, you will know the common saying yudan taiteki. That is my whole transmission; there is nothing else. This one phrase. Never forget it. Kyūsō then tells the story of King Wu of Zhou, newly enthroned, asking Taikōbō 太公望 for a rule brief enough to keep and lasting enough to hand down, and receiving the four lines of the 丹書, the Red Book: 敬勝怠者吉、怠勝敬者滅、義勝欲者従、欲勝義者凶, where care conquers negligence, good fortune; where negligence conquers care, ruin; where right conquers desire, obedience; where desire conquers right, disaster. And he concludes: 今油断大敵の語、鄙諺なれども丹書の戒に叶へり, the phrase yudan taiteki is a rustic proverb, but it agrees with the warning of the Red Book. Everyone knows carelessness is bad, he adds, and everyone hears the proverb without stopping at it, which is why they fail; Naotaka's distinction was that he never let it near him [12]. The 1894 typeset edition heads the chapter 大敵外になし, there is no enemy but this one [13].

Edo. The Edo いろはかるた. The card for ゆ is 油断大敵, and players added the tag 火がぼうぼう, and the fire roars [10]. Okada in 1958 reads the tag as if you do not look out, you may find your house on fire [14].

1910. Fujii Otoo 藤井乙男, 諺語大辞典. Four headwords in a row. 【油斷、强敵トナル】 pointing to the next, with 毛吹草 as its source; 【油斷大敵】 with Kyūsō's chapter compressed, his 鄙諺 become 俗話, then the Chinese classical company of the thought, 通俗編, 説苑, the 後漢書 on 患生于所忽、禍起于細微, trouble is born where it is neglected, disaster starts from small things, the 荀子 on 百事之成也、必在敬之、其敗也必在慢之, every undertaking succeeds by care and fails by neglect, and the 耳談続纂 on 慣熟之斧、乃傷厥跗, the familiar axe is the one that cuts your foot; then, unusually for this dictionary, two European proverbs, Delays are dangerous, marked Italian, and Danger comes soonest when it is despised, marked Latin; 【油斷ハ怪我ノ基】, carelessness is the root of injury, from the play 世継曽我; and 【油斷モスキモナラヌ】 [7].

The dictionaries today. デジタル大辞泉: 油断は失敗のもとであるから、大敵である。油断して失敗を招くのを戒めた言葉. 精選版日本国語大辞典: 油断は失敗のもとであるから、恐ろしい敵であるということ. ことわざを知る辞典: 油断は大敵と思っていましめよ。大丈夫だろうと気をゆるめて注意を怠ると、思いもよらない危険を招くことになる; 四字熟語を知る辞典 adds two uses, Dazai Osamu 太宰治 in 1933, たけは、油断大敵でせえ、と言っただけで, and Ishikawa Jun 石川淳 in 1949. The National Diet Library's full-text index holds twenty-three thousand eight hundred and seven items for the four characters, one thousand eight hundred and thirty-seven of them dated 1912 or earlier; one thousand eight hundred and one for the reading in kana; and two hundred and forty-four for the older 油断強敵 [10][15].

What is not a source. The proverb is Japanese, and the Chinese lines the 1910 dictionary sets beside it, the 丹書's 敬勝怠者吉, the 荀子's 必在敬之, the 説苑's 患生于所忽, are the classical company of the thought, given in the dictionary's habit, not its source; neither the Chinese Buddhist canon nor Chinese Wikisource carries the proverb. Kyūsō himself said so: a rustic proverb that happens to agree with the Red Book. The sutra's oil bowl is a story about the word 油断, told by one dictionary as the origin some give, and a page may tell it as a story so long as it says so. Of Fujii's two European proverbs, the Latin one, Danger comes soonest when it is despised, is a fair match and the Italian, Delays are dangerous, is a different proverb.

The proverb in English

1867. James Curtis Hepburn, A Japanese and English Dictionary, page 544. Under YU-DAN, negligence, inattention, slothfulness, heedlessness, carelessness, remissness, the sub-entry — tai-teki, negligence is a great enemy, (prov.). The first English print, and exact [2].

1889. Solomon Caesar Malan, Original Notes on the Book of Proverbs, volume two, page 611. On Proverbs 19:16, after a Telugu proverb on advice that does not keep: To which the Japanese add: "Carelessness is a great enemy." The footnote reads only Jap. pr. The rendering Buchanan printed seventy-six years later [3].

1896. Clay MacCauley, An Introductory Course in Japanese, pages 214 and 469. The thirty-ninth of the book's proverbs, ゆだんたいてき, glossed word by word, Negligence great enemy, then Negligence is a great enemy, and later a whole conversation built on it [16].

1896. F. Brinkley, F. Nanjō and Y. Iwasaki, An Unabridged Japanese-English Dictionary, page 1420. Under Taiteki, marked as a proverb and as literal: Yudan taiteki … negligence is a powerful enemy [17].

1915. Saitō Hidesaburō 斎藤秀三郎, Saito's Idiomological English-Japanese Dictionary, page 1184. Under Security: Security is the greatest enemy, 油断大敵. The English-Japanese side meets the proverb with an English line of its own, and Kenkyūsha's New English-Japanese Dictionary of 1980 gives the same line under security, with 油断大敵 and cf. Shak., Macbeth III.v.32–33, where the line is security / Is mortals' chiefest enemy [18][19].

1958. Rokuo Okada, Japanese Proverbs and Proverbial Phrases, page 182. Yudan taiteki. Negligence is a great foe, with the karuta's tag, hi ga bobo (on fire, in flames), meaning that if you do not look out, you may find your house on fire, and the English There's many a slip 'twixt the cup and the lip [14].

1963. Gordon W. Prange, Tora, Tora, Tora!, condensed in The Reader's Digest, November 1963. Of Admiral Nagumo turning his fleet for home after the attack on Pearl Harbor: Like Yamamoto he had a ready supply of Japanese maxims and proverbs. "Yudan taiteki," he said now. ("Carelessness is the greatest enemy.") The earliest rendering of the proverb with carelessness and the greatest that the Internet Archive's full text finds; the superlative is the translator's, since 大敵 is a great enemy [4].

1965. Daniel Crump Buchanan, Japanese Proverbs and Sayings, University of Oklahoma Press, page 42. Yudan taiteki: "Carelessness is a great enemy." The Japanese word "yudan" translated "carelessness" or "incaution," literally means "without oil." Hence, it can be appropriately applied to the five foolish virgins in the New Testament narrative. See Matthew 25:1-13. The rendering is exact, and Malan's. The etymology is not: 油断 does not literally mean without oil, the 精選版日本国語大辞典 marks its origin unknown and デジタル大辞泉 prints the sutra's oil bowl as one of two stories, and the parable of the virgins is Buchanan's own bridge from a folk etymology to a Christian text [20].

The proverb is not in David Galef's Even Monkeys Fall from Trees (Tuttle, 1987), Even a Stone Buddha Can Talk (Tuttle, 2000) or Japanese Proverbs (Tuttle, 2012), Guy Zona's Even Withered Trees Give Prosperity to the Mountain (1996) or Edward Trimnell's Tigers, Devils, and Fools (2004); Trimnell uses the word carelessness only under even monkeys fall from trees.

Today. The house title, Carelessness is one's greatest enemy, is Prange's line of 1963 with one's for the; the gloss:, Carelessness is a great enemy, is the Japanese word for word, and Malan's and Buchanan's. The two differ in one word: greatest reads 大 as a superlative, where the Japanese says a great enemy. The legacy record's three glosses, Unpreparedness is one's greatest enemy; He that is too secure is not safe; Overconfidence can be dangerous, cover the ground between them: the literal shape, an English proverb Thomas Fuller printed in 1732 [21], and the everyday paraphrase. What a rendering must keep: the enemy, because the proverb's whole force is that an inward lapse is treated as an outward foe; and a word for 油断 that means a dropped guard rather than a bad habit.

A reading

The proverb is a warning and not a creed, and it has always belonged as much to the soldier as to the householder: the chronicle tells it of a camp that posted no watch, Kyūsō of a statesman, Prange of an admiral sailing home, and the Edo card of a house on fire. Ii Naotaka's one-phrase transmission is short, quotable and true to a named source. The sutra's oil bowl is a legend of the word, and can be told as one.

Sources not seen

A reader with access to any of these is invited to write to Takase Studios at Tim@Takase.com.

References

  1. 「油断」, デジタル大辞泉・精選版 日本国語大辞典, at kotobank. https://kotobank.jp/word/油断-651959
  2. James Curtis Hepburn, A Japanese and English Dictionary, American Presbyterian Mission Press, Shanghai, 1867, p. 544, s.v. YU-DAN. Internet Archive japaneseenglishd00hepb, leaf n561. https://archive.org/details/japaneseenglishd00hepb/page/n561/mode/1up
  3. Solomon Caesar Malan, Original Notes on the Book of Proverbs, vol. 2, Williams and Norgate, London, 1889, p. 611, on Proverbs 19:16. Internet Archive originalnotesonb02mala. https://archive.org/details/originalnotesonb02mala
  4. Gordon W. Prange, Tora, Tora, Tora!, condensed in The Reader's Digest, November 1963 (the second of two instalments). Internet Archive sim_readers-digest_1963-11_83_499 (lending). https://archive.org/details/sim_readers-digest_1963-11_83_499 · the same text in the Indian edition, February 1964, Internet Archive in.ernet.dli.2015.100916. https://archive.org/details/in.ernet.dli.2015.100916
  5. 「甲陽軍鑑」, デジタル大辞泉・精選版 日本国語大辞典・改訂新版 世界大百科事典, at kotobank. https://kotobank.jp/word/甲陽軍鑑-63301
  6. 『甲陽軍鑑』品第二十三, 甲陽叢書, 温故堂, 1892–93, National Diet Library pid 899828, scan 78. https://dl.ndl.go.jp/pid/899828/1/78
  7. 藤井乙男『諺語大辞典』, 有朋堂, 1910 — 【油斷、强敵トナル】〔毛吹草〕 and 【油斷大敵】, National Diet Library pid 862766, scan 537. https://dl.ndl.go.jp/pid/862766/1/537 · 藤井乙男『諺の研究』, 1929, p. 240 (江戶時代に最も早く諺を蒐集したものは毛吹草で、之に次いで世話盡がある). National Diet Library pid 1452761, scan 127 · the same book's reproduction of the 毛吹草's 世話付古語, pp. 296–297 (ゆだん强敵となる on p. 297), scan 155. https://dl.ndl.go.jp/pid/1452761/1/127 · https://dl.ndl.go.jp/pid/1452761/1/155
  8. 松江重頼『毛吹草』, 岩波文庫, 1943, National Diet Library pid 1128297, scans 55 and 196 (excerpts only). https://dl.ndl.go.jp/pid/1128297/1/55 · the print of 1645, Waseda University Library 文庫18 00042. https://www.wul.waseda.ac.jp/kotenseki/html/bunko18/bunko18_00042/index.html
  9. 「油断強敵」, 精選版 日本国語大辞典, and 「わらんべ草」, デジタル大辞泉・精選版 日本国語大辞典, at kotobank. https://kotobank.jp/word/油断強敵-2090485 · https://kotobank.jp/word/わらんべ草-154339
  10. 「油断大敵」, デジタル大辞泉・精選版 日本国語大辞典・ことわざを知る辞典・四字熟語を知る辞典, at kotobank. https://kotobank.jp/word/油断大敵-651960
  11. 『やふにまくは』, 1718, National Diet Library pid 2568482, scan 10. https://dl.ndl.go.jp/pid/2568482/1/10
  12. 室鳩巣『駿台雑話』巻四, written 1732, printed 1750, National Diet Library pid 2559323, scan 62. https://dl.ndl.go.jp/pid/2559323/1/62
  13. 室鳩巣『駿台雑話』巻四, the 1894 typeset edition, National Diet Library pid 754747, scan 109. https://dl.ndl.go.jp/pid/754747/1/109
  14. Rokuo Okada, Japanese Proverbs and Proverbial Phrases, Japan Travel Bureau, Tokyo, 1958, p. 182, s.v. Yudan taiteki.
  15. National Diet Library Digital Collections, full-text index, oldest first: 油断大敵 (23,807 items), ゆだんたいてき (1,801), 油断強敵 (244). https://dl.ndl.go.jp/search/searchResult?keyword=油断大敵&fulltext=true&sortKey=ISSUED_ASC
  16. Clay MacCauley, An Introductory Course in Japanese, Kelly and Walsh, Yokohama, 1896, pp. 214 and 469, the thirty-ninth proverb. Internet Archive anintroductoryc00maccgoog, leaves n238 and n493. https://archive.org/details/anintroductoryc00maccgoog/page/n238
  17. F. Brinkley, F. Nanjō and Y. Iwasaki, An Unabridged Japanese-English Dictionary, Sanseidō, Tokyo, 1896, p. 1420, s.v. Taiteki. Internet Archive cu31924082117288, leaf n1451. https://archive.org/details/cu31924082117288/page/n1451
  18. 斎藤秀三郎, Saito's Idiomological English-Japanese Dictionary (熟語本位英和中辞典), S.E.G. Publishing Department, Tokyo, 1915, p. 1184, s.v. Security.
  19. Kenkyusha's New English-Japanese Dictionary, fifth edition, Kenkyūsha, Tokyo, 1980, s.v. security; the Macbeth line as Burton Stevenson, The Home Book of Quotations, fourth edition, 1944, prints it, s.v. Security.
  20. Daniel Crump Buchanan, Japanese Proverbs and Sayings, University of Oklahoma Press, Norman, 1965, p. 42.
  21. Thomas Fuller, Gnomologia, 1732, no. 2195, as Burton Stevenson, The Home Book of Proverbs, Maxims and Familiar Phrases, Macmillan, 1948, prints it.

Authors

Tim Jackowski (Systems Architect, Takase Studios, LLC) · 典 Ten (Anthropic Claude Fable 5.1, Takase Studios, LLC)

AI written · Ten wrote the history. Tim Jackowski commissioned it and answers for it.

Checked · grok-4.6 (xAI), 2026-09-05, citations · gpt-6-astra (OpenAI), 2026-09-05, citations

Cite as: Tim Jackowski and Ten, "Philology of 油断大敵 (yudan taiteki)," Takase Studios, 2026, https://takase.com/library/philology/yudan-taiteki.