rest　of　the　army；　on　the　further　bank；　also　scattered　and　fled　in
  all　directions。＇
  5。　　If　you　are　anxious　to　fight；　you　should　not　go　to　meet
  the　invader　near　a　river　which　he　has　to　cross。
  ＇For　fear　of　preventing　his　crossing。＇
  6。　　Moor　your　craft　higher　up　than　the　enemy；　and　facing　the
  sun。
  ＇See　supra；　　ss。　　2。　　The　repetition　of　these　words　in
  connection　with　water　is　very　awkward。　　Chang　Yu　has　the　note：
  〃Said　either　of　troops　marshaled　on　the　river…bank；　or　of　boats
  anchored　in　the　stream　itself；　in　either　case　it　is　essential　to
  be　higher　than　the　enemy　and　facing　the　sun。〃　　　The　other
  commentators　are　not　at　all　explicit。＇
  Do　not　move　up…stream　to　meet　the　enemy。
  ＇Tu　Mu　says：　　〃As　water　flows　downwards；　we　must　not　pitch
  our　camp　on　the　lower　reaches　of　a　river；　for　fear　the　enemy
  should　open　the　sluices　and　sweep　us　away　in　a　flood。　　Chu…ko　Wu…
  hou　has　remarked　that　'in　river　warfare　we　must　not　advance
  against　the　stream；'　which　is　as　much　as　to　say　that　our　fleet
  must　not　be　anchored　below　that　of　the　enemy；　for　then　they　would
  be　able　to　take　advantage　of　the　current　and　make　short　work　of
  us。〃　　There　is　also　the　danger；　noted　by　other　commentators；　that
  the　enemy　may　throw　poison　on　the　water　to　be　carried　down　to
  us。＇
  So　much　for　river　warfare。
  7。　　In　crossing　salt…marshes；　your　sole　concern　should　be　to
  get　over　them　quickly；　without　any　delay。
  ＇Because　of　the　lack　of　fresh　water；　the　poor　quality　of　the
  herbage；　and　last　but　not　least；　because　they　are　low；　flat；　　and
  exposed　to　attack。＇
  8。　　If　forced　to　fight　in　a　salt…marsh；　　you　should　have
  water　and　grass　near　you；　and　get　your　back　to　a　clump　of　trees。
  ＇Li　Ch‘uan　remarks　that　the　ground　is　less　likely　to　be
  treacherous　where　there　are　trees；　while　Tu　Mu　says　that　they
  will　serve　to　protect　the　rear。＇
  So　much　for　operations　in　salt…marches。
  9。　　In　dry；　level　country；　take　up　an　easily　accessible
  position　with　rising　ground　to　your　right　and　on　your　rear；
  ＇Tu　Mu　quotes　T‘ai　Kung　as　saying：　　〃An　army　should　have　a
  stream　or　a　marsh　on　its　left；　and　a　hill　or　tumulus　on　its
  right。〃＇
  so　that　the　danger　may　be　in　front；　and　safety　lie　behind。　　So
  much　for　campaigning　in　flat　country。
  10。　　These　are　the　four　useful　branches　of　　　military
  knowledge
  ＇Those；　　namely；　concerned　with　（1）　mountains；　　（2）　　rivers；
  （3）　　marshes；　　and　　（4）　　plains。　　Compare　Napoleon's　　〃Military
  Maxims；〃　no。　1。＇
  which　enabled　the　Yellow　Emperor　to　vanquish　four　several
  sovereigns。
  ＇Regarding　the　〃Yellow　Emperor〃：　　Mei　Yao…ch‘en　asks；　　with
  some　plausibility；　　whether　there　is　an　error　in　the　text　as
  nothing　is　known　of　Huang　Ti　having　conquered　four　other
  Emperors。　　The　SHIH　CHI　（ch。　1　ad　init。）　speaks　only　of　his
  victories　over　Yen　Ti　and　Ch‘ih　Yu。　　In　the　LIU　T‘AO　it　is
  mentioned　that　he　　〃fought　seventy　battles　and　pacified　the
  Empire。〃　　　Ts‘ao　Kung's　explanation　is；　that　the　Yellow　Emperor
  was　the　first　to　institute　the　feudal　system　of　vassals　princes；
  each　of　whom　（to　the　number　of　four）　originally　bore　the　title　of
  Emperor。　　Li　Ch‘uan　tells　us　that　the　art　of　war　originated　under
  Huang　Ti；　who　received　it　from　his　Minister　Feng　Hou。＇
  11。　　All　armies　prefer　high　ground　to　low。
  ＇〃High　Ground；〃　　says　Mei　Yao…ch‘en；　　〃is　not　only　more
  agreement　and　salubrious；　but　more　convenient　from　a　military
  point　of　view；　low　ground　is　not　only　damp　and　unhealthy；　　but
  also　disadvantageous　for　fighting。〃＇
  and　sunny　places　to　dark。
  12。　　If　you　are　careful　of　your　men；
  ＇Ts‘ao　Kung　says：　　〃Make　for　fresh　water　and　pasture；　　where
  you　can　turn　out　your　animals　to　graze。〃＇
  and　camp　on　hard　ground；　the　army　will　be　free　from　disease　of
  every　kind；
  ＇Chang　Yu　says：　　〃The　dryness　of　the　climate　will　prevent
  the　outbreak　of　illness。〃＇
  and　this　will　spell　victory。
  13。　　When　you　come　to　a　hill　or　a　bank；　occupy　the　sunny
  side；　　with　the　slope　on　your　right　rear。　　Thus　you　will　at　once
  act　for　the　benefit　of　your　soldiers　and　utilize　the　natural
  advantages　of　the　ground。
  14。　　When；　in　consequence　of　heavy　rains　up…country；　a　river
  which　you　wish　to　ford　is　swollen　and　flecked　with　foam；　you　must
  wait　until　it　subsides。
  15。　　Country　in　which　there　are　precipitous　cliffs　with
  torrents　running　between；　deep　natural　hollows；
  ＇The　latter　defined　as　〃places　enclosed　on　every　side　by
  steep　banks；　with　pools　of　water　at　the　bottom。＇
  confined　places；
  ＇Defined　as　〃natural　pens　or　prisons〃　or　〃places　surrounded
  by　precipices　on　three　sideseasy　to　get　into；　but　hard　to　get
  out　of。〃＇
  tangled　thickets；
  ＇Defined　as　〃places　covered　with　such　dense　undergrowth　that
  spears　cannot　be　used。〃＇
  quagmires
  ＇Defined　as　〃low…lying　places；　so　heavy　with　mud　as　to　be
  impassable　for　chariots　and　horsemen。〃＇
  and　crevasses；
  ＇Defined　by　Mei　Yao…ch‘en　as　〃a　narrow　difficult　way　between
  beetling　cliffs。〃　　Tu　Mu's　note　is　〃ground　covered　with　trees　and
  rocks；　　and　intersected　by　numerous　ravines　and　pitfalls。〃　　　This
  is　very　vague；　　but　Chia　Lin　explains　it　clearly　enough　as　a
  defile　or　narrow　pass；　and　Chang　Yu　takes　much　the　same　view。　　On
  the　whole；　the　weight　of　the　commentators　certainly　inclines　to
  the　rendering　〃defile。〃　　But　the　ordinary　meaning　of　the　Chinese
  in　one　place　is　〃a　crack　or　fissure〃　and　the　fact　that　the
  meaning　of　the　Chinese　elsewhere　in　the　sentence　indicates
  something　in　the　nature　of　a　defile；　make　me　think　that　Sun　Tzu
  is　here　speaking　of　crevasses。＇
  should　be　left　with　all　possible　speed　and　not　approached。
  16。　　While　we　keep　away　from　such　places；　we　should　get　the
  enemy　to　approach　them；　while　we　face　them；　we　should　let　the
  enemy　have　them　on　his　rear。
  17。　　If　in　the　neighborhood　of　your　camp　there　should　be　any
  hilly　country；　ponds　surrounded　by　aquatic　grass；　hollow　basins
  filled　with　reeds；　or　woods　with　thick　undergrowth；　they　must　be
  carefully　routed　out　and　searched；　for　these　are　places　where　men
  in　ambush　or　insidious　spies　are　likely　to　be　lurking。
  ＇Chang　Yu　has　the　note：　　〃We　must　also　be　on　our　guard
  against　traitors　who　may　lie　in　close　covert；　secretly　spying　out
  our　weaknesses　and　overhearing　our　instructions。〃＇
  18。　　When　the　enemy　is　close　at　hand　and　remains　quiet；　　he
  is　relying　on　the　natural　strength　of　his　position。
  ＇Here　begin　Sun　Tzu's　remarks　on　the　reading　of　signs；　　much
  of　which　is　so　good　that　it　could　almost　be　included　in　a　modern
  manual　like　Gen。　Baden…Powell's　〃Aids　to　Scouting。〃＇
  19。　　When　he　keeps　aloof　and　tries　to　provoke　a　battle；　　he
  is　anxious　for　the　other　side　to　advance。
  ＇Probably　because　we　are　in　a　strong　position　from　which　he
  wishes　to　dislodge　us。　　〃If　he　came　close　up　to　us；　says　Tu　Mu；
  〃and　tried　to　force　a　battle；　he　would　seem　to　despise　us；　　and
  there　would　be　less　probability　of　our　responding　to　the
  challenge。〃＇
  20。　　If　his　place　of　encampment　is　easy　of　access；　　he　is
  tendering　a　bait。
  21。　　Movement　amongst　the　trees　of　a　forest　shows　that　the
  enemy　is　advancing。
  ＇Ts‘ao　Kung　explains　this　as　〃felling　trees　to　clear　a
  passage；〃　　and　Chang　Yu　says：　　〃Every　man　sends　out　scouts　to
  climb　high　places　and　observe　the　enemy。　　If　a　scout　sees　that
  the　trees　of　a　forest　are　moving　and　shaking；　he　may　know　that
  they　are　being　cut　down　to　clear　a　passage　for　the　enemy's
  march。〃＇
  The　appearance　of　a　number　of　screens　in　the　midst　of　thick　grass
  means　that　the　enemy　wants　to　make　us　suspicious。
  ＇Tu　Yu's　explanation；　borrowed　from　Ts‘ao　Kung's；　　is　as
  follows：　　　〃The　presence　of　a　number　of　screens　or　sheds　in　the
  midst　of　thick　vegetation　is　a　sure　sign　that　the　enemy　has　fled
  and；　　fearing　pursuit；　has　constructed　these　hiding…places　in
  order　to　make　us　suspect　an　ambush。〃　　It　appears　that　these
  〃screens〃　　were　hastily　knotted　together　out　of　any　long　grass
  which　the　retreating　enemy　happened　to　come　across。＇
  22。　　The　rising　of　birds　in　their　flight　is　the　sign　of　an
  ambuscade。
  ＇Chang　Yu's　explanation　is　doubtless　right：　　　〃When　birds
  that　are　flying　along　in　a　straight　line　suddenly　shoot　upwards；
  it　means　that　soldiers　are　in　ambush　at　the　spot　beneath。〃＇
  Startled　beasts　indicate　that　a　sudden　attack　is　coming。
  23。　　When　there　is　dust　rising　in　a　high　column；　it　is　the
  sign　of　chariots　advancing；　when　the　dust　is　low；　but　spread　over
  a　wide　area；　it　betokens　the　approach　of　infantry。
  ＇〃High　and　sharp；〃　　or　rising　to　a　peak；　　is　of　course
  somewhat　exaggerated　as　applied　to　dust。　　The　commentators
  explain　the　phenom