Does nationalism always unify people? why or why not? (3 sentences)

Nationalism unifies only when people see themselves as having a common identity or purpose. 

In the 19th century, when nationalism began to rise up as a powerful political force, it had the tendency either to unite or divide, depending on circumstances.  In areas like the Italian peninsula or the German states, there was a uniting power to the aspirations of nationalism, bringing people together into a unified Italy and a unified Germany.  But elsewhere, in areas like the Austrian Empire or the Ottoman Empire, nationalism tended to divide those territories as groups identifying themselves according to a common "national" or ethnic identity sought to break into their own independent nation-states.

Nationalism also had a tendency to divide people against anyone they saw as different within their nation.  So persons of Jewish ethnicity were seen as not belonging within the nations of Europe where they were living, and anti-Semitism grew stronger.  In response, the Jewish people embraced a nationalist vision of their own -- Zionism.  The Zionist movement brought Jewish people together in the hope of relocating to their ancestral land of Israel.  But not all Jews were on board with the Zionist idea, so even that wasn't an entirely unifying force.