Chien；　but　this　is　a　mistake；　for　we　read　in　both　the　old　and　the
  New　　　T‘ang　History　　（ch。　　58；　　fol。　　2　and　ch。　　89；　　fol。　　8
  respectively）　　that　he　escaped　and　lived　on　until　656。　　Li　I…chi
  played　a　somewhat　similar　part　in　203　B。C。；　when　sent　by　the　King
  of　Han　to　open　peaceful　negotiations　with　Ch‘i。　　He　has　certainly
  more　claim　to　be　described　a　〃doomed　spy〃；　for　the　king　of　Ch‘i；
  being　subsequently　attacked　without　warning　by　Han　Hsin；　　and
  infuriated　by　what　he　considered　the　treachery　of　Li　I…chi；
  ordered　the　unfortunate　envoy　to　be　boiled　alive。＇
  13。　　SURVIVING　SPIES；　finally；　are　those　who　bring　back　news
  from　the　enemy's　camp。
  ＇This　is　the　ordinary　class　of　spies；　properly　so　called；
  forming　a　regular　part　of　the　army。　　Tu　Mu　says：　　〃Your　surviving
  spy　must　be　a　man　of　keen　intellect；　though　in　outward　appearance
  a　fool；　of　shabby　exterior；　but　with　a　will　of　iron。　　He　must　be
  active；　　robust；　　endowed　with　physical　strength　and　courage；
  thoroughly　accustomed　to　all　sorts　of　dirty　work；　able　to　endure
  hunger　and　cold；　and　to　put　up　with　shame　and　ignominy。〃　　Ho　Shih
  tells　the　following　story　of　Ta‘hsi　Wu　of　the　Sui　dynasty：　　〃When
  he　was　governor　of　Eastern　Ch‘in；　Shen…wu　of　Ch‘i　made　a　hostile
  movement　upon　Sha…yuan。　　The　Emperor　T‘ai　Tsu　＇？　Kao　Tsu＇　　sent
  Ta…hsi　Wu　to　spy　upon　the　enemy。　　He　was　accompanied　by　two　other
  men。　　All　three　were　on　horseback　and　wore　the　enemy's　uniform。
  When　it　was　dark；　they　dismounted　a　few　hundred　feet　away　from
  the　enemy's　camp　and　stealthily　crept　up　to　listen；　　until　they
  succeeded　in　catching　the　passwords　used　in　the　army。　　Then　they
  got　on　their　horses　again　and　boldly　passed　through　the　camp
  under　the　guise　of　night…watchmen；　and　more　than　once；　　happening
  to　come　across　a　soldier　who　was　committing　some　breach　of
  discipline；　　they　actually　stopped　to　give　the　culprit　a　sound
  cudgeling！　　Thus　they　managed　to　return　with　the　fullest　possible
  information　about　the　enemy's　dispositions；　and　received　warm
  commendation　from　the　Emperor；　who　in　consequence　of　their　report
  was　able　to　inflict　a　severe　defeat　on　his　adversary。〃＇
  14。　　Hence　it　is　that　which　none　in　the　whole　army　are　more
  intimate　relations　to　be　maintained　than　with　spies。
  ＇Tu　Mu　and　Mei　Yao…ch‘en　point　out　that　the　spy　is
  privileged　to　enter　even　the　general's　private　sleeping…tent。＇
  None　should　be　more　liberally　rewarded。　　In　no　other　business
  should　greater　secrecy　be　preserved。
  ＇Tu　Mu　gives　a　graphic　touch：　　all　communication　with　spies
  should　be　carried　〃mouth…to…ear。〃　　The　following　remarks　on　spies
  may　be　quoted　from　Turenne；　who　made　perhaps　larger　use　of　them
  than　any　previous　commander：　　〃Spies　are　attached　to　those　who
  give　them　most；　　he　who　pays　them　ill　is　never　served。　　They
  should　never　be　known　to　anybody；　nor　should　they　know　one
  another。　　When　they　propose　anything　very　material；　secure　their
  persons；　　or　have　in　your　possession　their　wives　and　children　as
  hostages　for　their　fidelity。　　Never　communicate　anything　to　them
  but　what　is　absolutely　necessary　that　they　should　know。　＇2＇　＇
  15。　　Spies　cannot　be　usefully　employed　without　a　certain
  intuitive　sagacity。
  ＇Mei　Yao…ch‘en　says：　　〃In　order　to　use　them；　one　must　know
  fact　from　falsehood；　and　be　able　to　discriminate　between　honesty
  and　double…dealing。〃　　　Wang　Hsi　in　a　different　interpretation
  thinks　more　along　the　lines　of　　〃intuitive　perception〃　　and
  〃practical　　　intelligence。〃　　　　Tu　Mu　strangely　　　refers　　　these
  attributes　to　the　spies　themselves：　　〃Before　using　spies　we　must
  assure　ourselves　as　to　their　integrity　of　character　and　the
  extent　of　their　experience　and　skill。〃　　But　he　continues：　　　〃A
  brazen　face　and　a　crafty　disposition　are　more　dangerous　than
  mountains　or　rivers；　it　takes　a　man　of　genius　to　penetrate　such。〃
  So　that　we　are　left　in　some　doubt　as　to　his　real　opinion　on　the
  passage。〃＇
  16。　　They　cannot　be　properly　managed　without　benevolence　and
  straightforwardness。
  ＇Chang　　　Yu　says：　　　〃When　you　have　attracted　　　them　　　by
  substantial　offers；　you　must　treat　them　with　absolute　sincerity；
  then　they　will　work　for　you　with　all　their　might。〃＇
  17。　　Without　subtle　ingenuity　of　mind；　　one　cannot　make
  certain　of　the　truth　of　their　reports。
  ＇Mei　Yao…ch‘en　says：　　　〃Be　on　your　guard　against　　　the
  possibility　of　spies　going　over　to　the　service　of　the　enemy。〃＇
  18。　　Be　subtle！　be　subtle！　and　use　your　spies　for　every　kind
  of　business。
  ＇Cf。　VI。　ss。　9。＇
  19。　　If　a　secret　piece　of　news　is　divulged　by　a　spy　before
  the　time　is　ripe；　he　must　be　put　to　death　together　with　the　man
  to　whom　the　secret　was　told。
  ＇Word　for　word；　the　translation　here　is：　　〃If　spy　matters
  are　heard　before　＇our　plans＇　are　carried　out；〃　etc。　　Sun　Tzu's
  main　point　in　this　passage　is：　　Whereas　you　kill　the　spy　himself
  〃as　a　punishment　for　letting　out　the　secret；〃　　the　object　of
  killing　the　other　man　is　only；　as　Ch‘en　Hao　puts　it；　〃to　stop　his
  mouth〃　　and　prevent　news　leaking　any　further。　　If　it　had　already
  been　repeated　to　others；　this　object　would　not　be　gained。　　Either
  way；　　Sun　Tzu　lays　himself　open　to　the　charge　of　inhumanity；
  though　Tu　Mu　tries　to　defend　him　by　saying　that　the　man　deserves
  to　be　put　to　death；　for　the　spy　would　certainly　not　have　told　the
  secret　unless　the　other　had　been　at　pains　to　worm　it　out　of
  him。〃＇
  20。　　Whether　the　object　be　to　crush　an　army；　　to　storm　a
  city；　or　to　assassinate　an　individual；　it　is　always　necessary　to
  begin　by　finding　out　the　names　of　the　attendants；　the　aides…de…
  camp；
  ＇Literally　　〃visitors〃；　　is　equivalent；　as　Tu　Yu　says；　　to
  〃those　whose　duty　it　is　to　keep　the　general　supplied　with
  information；〃　　which　naturally　necessitates　frequent　interviews
  with　him。＇
  and　door…keepers　and　sentries　of　the　general　in　command。　　Our
  spies　must　be　commissioned　to　ascertain　these。
  ＇As　the　first　step；　no　doubt　towards　finding　out　if　any　of
  these　important　functionaries　can　be　won　over　by　bribery。＇
  21。　　The　enemy's　spies　who　have　come　to　spy　on　us　must　be
  sought　out；　tempted　with　bribes；　led　away　and　comfortably　housed。
  Thus　they　will　become　converted　spies　and　available　for　our
  service。
  22。　　It　is　through　the　information　brought　by　the　converted
  spy　that　we　are　able　to　acquire　and　employ　local　and　inward
  spies。
  ＇Tu　Yu　says：　　〃through　conversion　of　the　enemy's　spies　we
  learn　the　enemy's　condition。〃　　And　Chang　Yu　says：　　〃We　must　tempt
  the　converted　spy　into　our　service；　because　it　is　he　that　knows
  which　of　the　local　inhabitants　are　greedy　of　gain；　and　which　of
  the　officials　are　open　to　corruption。〃＇
  23。　　It　is　owing　to　his　information；　again；　　that　we　can
  cause　the　doomed　spy　to　carry　false　tidings　to　the　enemy。
  ＇Chang　Yu　says；　〃because　the　converted　spy　knows　how　the
  enemy　can　best　be　deceived。〃＇
  24。　Lastly；　it　is　by　his　information　that　the　surviving　spy
  can　be　used　on　appointed　occasions。
  25。　　The　end　and　aim　of　spying　in　all　its　five　varieties　is
  knowledge　of　the　enemy；　and　this　knowledge　can　only　be　derived；
  in　the　first　instance；　from　the　converted　spy。
  ＇As　explained　in　ss。　22…24。　　He　not　only　brings　information
  himself；　　but　makes　it　possible　to　use　the　other　kinds　of　spy　to
  advantage。＇
  Hence　it　is　essential　that　the　converted　spy　be　treated　with　the
  utmost　liberality。
  26。　Of　old；　the　rise　of　the　Yin　dynasty
  ＇Sun　Tzu　means　the　Shang　dynasty；　founded　in　1766　B。C。　　Its
  name　was　changed　to　Yin　by　P‘an　Keng　in　1401。
  was　due　to　I　Chih
  ＇Better　known　as　I　Yin；　the　famous　general　and　statesman
  who　took　part　in　Ch‘eng　T‘ang's　campaign　against　Chieh　Kuei。＇
  who　had　served　under　the　Hsia。　　Likewise；　the　rise　of　the　Chou
  dynasty　was　due　to　Lu　Ya
  ＇Lu　Shang　rose　to　high　office　under　the　tyrant　Chou　Hsin；
  whom　he　afterwards　helped　to　overthrow。　　Popularly　known　as　T‘ai
  Kung；　　a　title　bestowed　on　him　by　Wen　Wang；　he　is　said　to　have
  composed　a　treatise　on　war；　erroneously　identified　with　the
  LIU　T‘AO。＇
  who　had　served　under　the　Yin。
  ＇There　is　less　precision　in　the　Chinese　than　I　have　thought
  it　well　to　introduce　into　my　translation；　and　the　commentaries　on
  the　passage　are　by　no　means　explicit。　　But；　having　regard　to　the
  context；　　we　can　hardly　doubt　that　Sun　Tzu　is　holding　up　I　Chih
  and　Lu　Ya　as　illustrious　examples　of　the　converted　spy；　　or
  something　closely　analogous。　　His　suggestion　is；　that　the　Hsia
  and　Yin　dynasties　were　upset　owing　to　the　intimate　knowledge　of
  their　weaknesses　and　shortcoming　which　these　former　ministers
  were　able　to　impart　to　the　other　side。　　Mei　Yao…ch‘en　appears　to
  resent　any　such　aspersion　on　these　historic　names：