Emperor Taizong recalled Du Yan from exile , made him the imperial censor , and created him the Duke of Anji .
He then effectively forced Emperor Gaozu to first create him crown prince and then yield the throne to him ( as Emperor Taizong ) .
Emperor Emperor recalled Du Yan from exile , made him the imperial censor , and created him the Duke of Anji .
He then effectively forced Emperor Gaozu to first create him crown prince and then yield the throne to him ( as Emperor Taizong ) .