В книге, в значительной степени определившей фантастику ХХ века

...бизнесмен, востоковед и астроном Персиваль Лоуэлл писал:

"The first thing that is forced on us in conclusion is the necessarily intelligent and non-bellicose character of the community which could thus act as a unit through-out its globe. War is a survival among us from savage times and affects now chiefly the boyish and unthinking element of the nation. The wisest realize that there are better ways for practicing heroism and other and more certain ends of insuring the survival of the fittest. It is something a people outgrow. But whether they consciously practice peace or not, nature in its evolution eventually practices it for them, and after enough of the inhabitants of a globe have killed each other off, the remainder must find it more advantageous to work together for the common good."

(Lowell P. Mars and its canals, New York: The Macmillan company; London, Macmillan, 1906, P. 377)

Глядя на воображаемое состояние старого мудрого Марса, покрытого глобальной сетью каналов, Лоуэлл полагал, что "Человечество перерастает войну"... До начала Первой мировой оставалось 8 лет, Лоуэлл ее застал.
А в фантастике темы войн и поныне доминируют...