h　to　cover　it。　If　we　pursue　we　shall　fall　victims。　Let　him　go　in　peace；　and　I　shall　then　get　through　the　Xie　Valley　and　take　Qishan；　making　use　of　the　enemy's　lack　of　defense。〃

〃But　there　are　other　ways　of　taking　Changan；〃　said　they。　〃Why　only　take　Qishan？〃

〃Because　Qishan　is　the　first　step　to　Changan；　and　I　want　to　gain　the　advantage　of　position。　And　every　transportation　from　the　West　Valley　Land　must　e　this　way。　It　rests　on　River　Wei　in　front　and　is　backed　by　the　Xie　Valley。　It　gives　the　greatest　freedom　of　movement　and　is　a　natural　maneuvering　ground。　That　is　why　I　want　it。〃

They　bowed　to　his　wisdom。

Then　Zhuge　Liang　dispatched　Wei　Yan；　Zhang　Ni；　Du　Qiong；　and　Chen　Shi　for　Gu　Valley；　and　he　sent　Ma　Dai；　Wang　Ping；　Zhang　Yi；　and　Ma　Zheng　for　the　Xie　Valley；　all　were　to　meet　at　the　Qishan　Mountains。　He　led　the　main　army　himself；　with　Guan　Xing　and　Liao　Hua　in　the　van。

When　the　Wei　army　retreated；　Cao　Zhen　and　Sima　Yi　remained　in　the　rear　superintending　the　movement。　They　sent　a　reconnoitering　party　along　the　old　road　to　Chencang；　and　they　returned　saying　no　enemy　was　to　be　seen。　Ten　days　later　the　leaders；　who　had　manded　in　the　ambush；　joined　the　main　body　saying　that　they　had　seen　no　sign　of　the　enemy。

＇e＇　The　mountainous　roads　to　Shu　were　very　difficult。　People　had　to　lay　planks　on　the　earth　to　make　roads。

Cao　Zhen　said；　〃This　continuous　autumn　rain　has　rendered　all　the　plank　trails*　impassable。　How　could　the　soldiers　of　Shu　know　of　our　retreat？〃

〃They　will　appear　later；〃　said　Sima　Yi。

〃How　can　you　know？〃

〃These　late　five　dry　days　they　have　not　pursued；　because　they　think　we　shall　have　left　a　rearguard　in　ambush。　Therefore　they　have　let　us　get　well　away。　But　after　we　have　gone；　they　will　try　to　occ