Allegedly, accordingly to the following analyst with 40+ years experience in the region, the Saudi backed Yemeni government troops numbered tens of thousands on paper, but in reality were only 3000. Even then, those forces didn’t really want to fight.
The South Yemenis were well equipped, but poorly trained, motivated, and led.
IMHO, other than a general mobilization by the Saudis of 100,000 Saudi men (from across all of Saudi tribal society) or an equally sized well trained army of foreigners, the only other option for the Saudis will be to rebuild their pipeline, get awacs to fly over their pipeline and bring in a lot of air defenses. (BTW, if the Saudis really did mobilize a 100,000 man army as the analyst in the video suggests, taking the Red Sea coast back and holding the terrain would be most of the objective; surrounding and cutoff the Houthi allied population, but not going into those mountains and being decimated like the Egyptians were decades ago.)
This might be an existential moment for the Saudi economy.
In the meantime, the Houthis will be planning to race to take Aden, while there is confusion. Saudis could rally their Yemeni allies to reinforce and built up the defenses around Aden, to stop the momentum of the Houthi offensive. As for ISR, Saudis could put up enough drones to watch for advancing troops, the real issue is command and control. Who would be leading any defense of Aden?
Frankly, no one is willing to fight for the Saudis under the current arrangements Saudi has for its allies or its own citizens. The blowback from Iran is one reason, but so is the general lack of a political strategy.
P.S. some sources say the Houthis may have up to 300,000 troops. Classic military strategy says an attacker should number 3:1 for a full war. Considering Houthi controlled territory is 85% of the 40 million population of Yemen; 34 million, so with COIN 1:20 ratio, would mean between these two scenarios, a force of 900,000-1,700,000 to have a chance at completely taking out the Houthis.
Instead of Saudi’s NEOM line, the Saudis may need to retake the entire Red Sea coast and build a Ukrainian style “defense line” to hold it. But this would mean a full scale war.
In the mean time, IMHO, there is going to be a major naval and amphibious assault battle in the making. Saudi has a major helicopter lift capability. They could land a lot of troops, but they will face a lot of Houthi anti ship and air defenses, as well as mines.
You can also assume Saudi diplomats are going to reaching out to the Yemenis tribes allied to the Houthis to be peeled away.
