Why did Alfred North Whitehead disagree with Bertrand Russell’s pacifism during World War I?

Alfred North Whitehead was a pacific man, but he was not a pacifist. During World War I, he viewed the conflict as hideous but believed that England’s participation in it was necessary. Consequently, he regarded Bertrand Russell’s pacifism as simplistic.1

Despite this fundamental disagreement, their personal bond remained strong. After Russell was imprisoned for his antiwar campaigning, Whitehead visited him and maintained their friendship, demonstrating a level of tolerance that Russell later acknowledged was greater than what he could return.1