What was Confucius' attitude toward war.

Given the pillars of five principal relationships, it is self-evident that harmonious relationship is the central tenet here. Historically, countries around the sinosphere (Korea, Vietnam, Japan) understood even the relationship between themselves and China in the context of king (Chinese emperor) and his servant according to Mencius' teaching (以小事大). Confucius lived during the Spring and Autumn period, a turbulent epoch of time when you had states warring one another. There are 4 references to the word, "war" in the Analects. Let a good man teach the people seven years, and they may then likewise be employed in war.

To lead an uninstructed people to war, is to throw them away.

The things in reference to which the Master exercised the greatest caution were - fasting, war, and sickness.

The Duke Hwan assembled all the princes together, and that not with weapons of war and chariots. Although it could be implicit from the rest of his teachings that war would not happen in an ideal situation, it's most likely that he saw it as an inevitable part of life, therefore we read an instruction to prepare judiciously for war. Remember, it's likely that many of his disciples were future leaders and officials at various government positions.