 Complete the following phrase:  By early 1393 Turnovo Bulgarias Ivan Shishman, hoping to throw off his onerous vassalage, was in secret negotiations with Sigismund, along with Wallachian Voievod Mircea the Old 13861418 and, possibly, Vidins Ivan Sratsimir. Bayezid got wind of the talks and launched a devastating campaign against Shishman. Turnovo was captured after a 