Historical examples of secessionist movements fighting alongside their de jure governments

Question

In the complicated many-sided conflict in Mali, the MNLA, are fighting for a secular state in Azawad, whereas islamists (such as Ansar Dine), seek the imposition of Sharia law across Mali. Recently, France has intervened to prevent islamists from achieving their goals; see also this question.

As the Wikipedia article on the conflict summarises, Ansar Dine and MNLA initially cooperated, but have subsequently waged war because of disagreements about the nature their state should have, and MNLA are now "ready to help" their former opponents in the fight against the Islamists:

We can do the job on the ground. We’ve got men, arms and, above all, the desire to rid Azawad of terrorism.

^{Source: Al Arabiya}

Until recently, MNLA were fighting against the government of Mali, and now they are fighting with the government of Mali. This seems unusual, and I wonder what the consequences for their relation post-conflict may be. Are there any historical examples of armed secessionist groups joining arms with their de jure government to drive out a common enemy?

Answer 1

Anbar Awakening seems like a good model for what you seek. While not strictly speaking "secessionist", they fought against Iraqi gvernment; but then "grew tired" of transnational Jihadi "brothers in arms" and started supporting Iraqui government (and US military) against them (to oversimplify to the point of absurdity).

Answer 2

Communists and Kuomintang fighting together against the Japanese.