Why did Dr.Sado mutter the words 'my friend' while treating the american prisoner of war.What is ironical about these words?

While attending the wounded soldier, Dr. Sadao felt nice because he felt a sense of contentment. He knew that he was dedicating himself toward his duty. As a good doctor he always addressed his patients as friend and so while he was operating the soldier, he called him a friend.
These words were ironical to a certain extent because the soldier belonged to the enemy nation. He was fighting against Dr. Sadao’s nation. Moreover, being a loyal citizen, Dr. Sadao had thought of handing over the wounded soldier to his country.