The nations of West Africa are loosely affiliated under a supernational group called the Economic Community of West African States (ECOWAS), sort of like how most of Europe is affiliated under the EU. Up until recently, the members of ECOWAS were all democracies (though not necessarily very strong ones). Many of them have had significant security problems, especially in the relatively poor and inaccessible Sahel.
Starting in 2021, a series of military coups occurred in Mali, Guinea, and Burkina Faso. Those countries are now lead by military juntas. ECOWAS responded by suspending their memberships and pressuring them to return to democracy, to no avail.
Last month, another coup d'etat occurred in Niger (the sparsely populated arid nation, not to be confused with Nigeria, its massive neighbor to the south). At this point, it became clear that a) military coups are an existential risk to democracy in West Africa, and b) politely asking military juntas to return to democracy is not a productive strategy. ECOWAS gave the Nigerien junta one week to restore the democratically elected government or face military intervention. The junta ignored them. Today, ECOWAS voted to conduct a military intervention in Niger.
If this military intervention was limited to removing the Nigerien junta, it would be pretty straightforward, since they'd be massively outnumbered and outgunned. However, the juntas in Mali and Burkina Faso have indicated that they would also militarily intervene in Niger in support of the junta. (Guinea, the fourth junta nation, supports the Nigerien junta but is not expected to get involved in a war.) Military intervention is also not particularly popular with the general population, either in the democracies or the junta nations.
As such, there's a very real possibility that this could spiral into a nasty, heavily destabilizing regional war. It's hard to predict what will happen, but it's unlikely to be good.