Yemeni Forces advancing along the coastal plains without naval and air cover was never going to be sustainable. It makes them sitting ducks and sandwiches them in between an enemy that is entrenched in Hudaydah (from where they have access to the sea) and the mountainous range that acts like forts to their stronghold in Sa’dah and San’a. Which is why I highly doubt this was the plan in the first place. Keep your eyes on the Eastern front (Jawf, Ma’rib) 👀