Nationalism is the strong support of the rights and interests of one’s own country (without caring about what happens to other countries).
Strong nationalist elements led to the reunification of Italy in 1861 and
Germany in 1871. The settlement at the end of the Franco-Prussian War
left France angry at the loss of Alsace Lorraine to Germany and keen to
regain the lost territory. Large areas of both Austria-Hungary and Serbia
were home to differing nationalist groups, all of whom wanted freedom
from the states in which they lived.
How does this cause a war? PLZ HELP