Now　Cao　Zhen　still　remembered　bitterly　that　in　the　last　campaign　Sima　Yi　had　filched　from　him　the　credit　he　hoped　to　obtain。　So　when　he　received　the　mission　of　defending　the　capitals　against　the　invading　forces；　he　detached　Guo　Huai　and　Sun　Li　and　sent　them　to　hold　positions　east　and　west。　Then　he　had　heard　that　Chencang　was　threatened；　so　had　sent　Wang　Shuang　to　its　relief；　and　now　to　his　joy　he　heard　of　his　henchman's　success。　He　placed　Grand　mander　Fei　Yao　in　mand　of　the　van　and　stationed　other　generals　at　strategic　and　manding　points。

Then　they　caught　a　spy。　He　was　taken　into　the　presence　of　the　mander…in…Chief　to　be　questioned。

The　man　knelt　down　and　said；　〃I　am　not　really　a　spy　in　the　bad　sense。　I　was　bringing　a　secret　munication　for　you；　Sir；　but　I　was　captured　by　one　of　the　parties　in　ambush。　Pray　send　away　your　attendants。〃

The　man's　bonds　were　loosed　and　the　tent　cleared。

The　captive　said；　〃I　am　a　confidant　of　Jiang　Wei；　who　has　entrusted　me　with　a　secret　letter。〃

〃Where　is　the　letter？〃

The　man　took　it　from　among　his　garments　and　presented　it　to　Cao　Zhen；　who　read：

〃I；　Jiang　Wei；　your　guilty　general；　make　a　hundred　prostrations　to　the　great　leader　Cao　Zhen；　now　in　the　field。　I　have　never　forgotten　that　I　was　in　the　employment　of　Wei　and　disgraced　myself；　having　enjoyed　favors；　I　never　repaid　them。　Lately　I　have　been　an　unhappy　victim　of　Zhuge　Liang's　wiles　and　so　fell　into　the　depths。　But　I　never　forgot　my　old　allegiance。　How　could　I　forget？

〃Now　happily　the　army　of　Shu　has　gone　west；　and　Zhuge　Liang　trusts　me。　I　rely　upon　your　leading　an　army　this　way。　If　resistance　be　met；　then　you　may　simulate　defeat　and　retire；　but　I　shall　be　behind　and　will　make　a　blaze　as　signal。　Then　I　shall　set　fire　to　their　s