why dr. sadao was not able to kill the americn soldier though mericans were his enemy?

The dilemma that Sadao faced was a clash between his duties as a doctor and that as a citizen of a particular nation. He comments that if the man was whole, uninjured, then he would not have faced any difficulty in turning him over to the police. As a nation at war, America was the common enemy of all Japanese citizens and the enemy soldier was only a common fellow. However, the fact that he was wounded complicated this issue because as a doctor, Sadao had taken the oath to put those duties first and serve mankind as a whole, without any discriminations on the basis of nationality. As a wounded person, the American soldier was at his mercy and he found it impossible to refuse medical assistance in such a case.