The homotopy sequence of Noriʼs fundamental group

In this paper, we investigate the necessary and sufficient conditions for the exactness of the homotopy sequence of Noriʼs fundamental group and apply these to various special situations to regain some classical theorems and give a counterexample to show the conditions are not always satisfied. This work is partially based on the earlier work of H. Esnault, P.-H. Hai, E. Viehweg.