precipitous；　and　I　am　thinking　of　going　back。　What　think　you？〃

Guo　Jia　replied；　〃The　success　of　an　expedition　of　this　kind　depends　upon　celerity。　To　strike　a　sudden　blow　on　a　distant　spot　with　a　heavy　baggage　train　is　difficult。　To　ensure　success　the　need　is　light　troops　and　a　good　road　to　strike　quickly　before　an　enemy　has　time　to　prepare。　Now　you　must　find　guides　who　know　the　road　well。〃

Then　the　sick　adviser　was　left　at　Yezhou　for　treatment；　and　they　sought　among　the　natives　for　some　persons　to　serve　as　guides。　Tian　Chou；　one　of　Yuan　Shao's　old　generals；　knew　those　parts　well；　and　Cao　Cao　called　him　and　questioned　him。

Tian　Chou　said；　〃Between　autumn　and　summer　this　route　is　under　water；　the　shallow　places　too　heavy　for　wheeled　traffic；　the　deep　parts　insufficient　for　boats。　It　is　always　difficult。　Therefore　you　would　do　better　to　return　and　at　Lulong　cross　the　Baitan　Pass　into　the　desert。　Then　advance　to　Liucheng　and　smite　before　there　is　time　to　prepare。　One　sudden　rush　will　settle　King　Mao　Dun。〃

For　this　valuable　information　and　plan；　Tian　Chou　was　made　General　Who　Calms　the　North；　and　went　in　advance　as　leader　and　guide。　Next　after　him　came　Zhang　Liao；　and　Cao　Cao　brought　up　the　rear。　They　advanced　by　double　marches。

Tian　Chou　led　Zhang　Liao　to　White　Wolf　Hills；　where　they　came　upon　Yuan　Xi；　Yuan　Shang；　and　King　Mao　Dun　and　a　force　of　ten　thousand　cavalry。　Zhang　Liao　galloped　to　inform　his　chief；　and　Cao　Cao　rode　up　to　the　top　of　an　eminence　to　survey　the　foe。　He　saw　a　large　mass　of　cavalry　without　any　military　formation　advancing　in　a　disorderly　crowd。

Said　he；　〃They　have　no　formation。　We　can　easily　rout　them。〃

Then　he　handed　over　his　ensign　of　mand　to　Zhang　Liao　who；　with　Xu　Chu；　Yu　Jin；　and　Xu　Huang；　made　a　vig