Italy and France

In 1870, the Italian states were attempting to fight a war in order to unify. The main barrier to unification was the Austrian Empire to the north which sought to keep the Italian states separate and under Austrian influence. Since they couldn't fight Austria on their own, the Italians made a deal with France for support in their war. The French were under the idea that they would be getting a powerfully ally that favored France. However, upon the unification of Italy the Italians turned their back on their French supporters.

                 Soviet Union and Poland
As the Soviet Union started to beat back the Germans, the Polish resistance could feel their liberation coming. To expedite their liberation, the Polish launched the largest resistance operation in WWII, known today as the Warsaw Uprising. During this uprising, Poland actually managed to completely take Warsaw back from the Germans, and they timed this so that it would occur exactly as the Soviet Union reached the city. As the Soviet Union started to beat back the Germans, the Polish resistance could feel their liberation coming. To expedite their liberation, the Polish launched the largest resistance operation in WWII, known today as the Warsaw Uprising. During this uprising, Poland actually managed to completely take Warsaw back from the Germans, and they timed this so that it would occur exactly as the Soviet Union reached the city. The resistance was wiped out by the German army as the Soviets waited just outside the city.