Emmanuel_Capricorn
You know forming an alliance with Shen was actually the best strategic move. As Shens general. Tai lung knows about Sheba exact number and strength of his soldiers, his tactics, strongholds, weaponry and supplies. Plus as basically Sheba new right hand he can guide Shen in a better reaction or worst case use the information to minimise the impact. If he refused he could have easily turned his army/weapons on him and devastated the city and everyone in it. Not to mention giving him the possibility of redemption.