How was nationalism a driving force behind the unification of Germany and Italy?

Nationalism is a unifying effect when it comes to history. Areas with similar languages and values have a lot to say, when you see that much is similar you realize that it is often better together. In Germany, the pus factor was Prussia's expansionism that might start it. This is similar to Italy, where several people speak the same language and share the same values.

the triple alliance. germany and austria-hungary were already allies by 1879 when, worried about a threat from russia, they formed the dual alliance. italy joined the group in 1882. there was a concern about a possible attack from france and the alliance needed powerful friends to defend it.