Reuters: Yemen’s southern separatists attack military academy in Aden. Quoting,

Southern separatists opened fire on a military academy graduation ceremony in Yemen’s port city of Aden on Saturday, killing a cadet and wounding at least two others, witnesses said. … The incident is the latest in a series of killings and bombings in the southern city…

Yemen, Saleh (Now Dead), and Civil War, Part 2 anticipates a tertiary conflict. Quoting,

There are actually three conflicts:

• Primary. Houthi versus non-Houthi.
• Secondary. north versus south.
• Tertiary, potential.  Zaydi versus Sunni in the north.

Instead of the tertiary conflict, the secondary has become active. The original prediction was based on the passivity of northern Sunnis towards the tradition of Zaydi governance.

We need a friends-and-enemies table to sort this out:

• All Zaydis are Shia. These are religious terms.
• Most Houthis are Zaydis. Houthis are a movement, not a religion.
• Not all Zaydis are Houthis, and not all Houthis are Zaydis.
• Saleh, like almost all the rulers of Yemen,  was Zaydi, but an active enemy of the Houthis (mostly of the same religion), until his fall from power.  When the Houthis overthrew Mansour Hadi, Saleh allied with the Houthis to regain some power.
• Mansour Hadi is a southern Sunni.
• The southern separatists, the same region and religion as Hadi, have attacked the “government” forces of which Hadi is the titular head.

This makes no sense unless one concludes that the conflict, cloaked as sectarian struggle, is actually a tribal conflict over the scarce resources necessary for life.

What remains for the tertiary conflict to become active? For the military situation, refer to Yemen Hodeidah Assault and  (Middle East Eye, 7/26)  Stalemate in Yemen: Why has the battle for Hodeidah ground to a halt? As long as the Houthis stalemate the Saudi coalition, they are not clearly losers. Should this resolve in the favor of the coalition, it is likely that the tertiary conflict will activate.