What humor does Henry see as he is reflected in Chapter 8 ?

From the text:

Reflecting, he saw a sort of a humor in the point of view of himself and his fellows during the late encounter. They had taken themselves and the enemy very seriously and had imagined that they were deciding the war. Individuals must have supposed that they were cutting the letters of their names deep into everlasting tablets of brass, or enshrining their reputations forever in the hearts of their countrymen, while, as to fact, the affair would appear in printed reports under a meek and immaterial title.