The basic idea behind the war on Yemen, at least on the geopolitical level, and not on the level of what’s effectively political semantics when you discuss whether or not Abdrabbuh Mansur Hadi is the legitimate President seeing as he resigned and later rescinded his resignation, basically goes like this: 

- Iran controls the Ansar Allah…why? Well, because Iran is Shia Muslim and they’re Shia Muslim, of course! (Never mind the fact that they’re from a completely different branch of Shia Islam, it’s the label that counts)

- Iran is directing the Ansar Allah to destabilize Saudi Arabia’s “backyard”.

- Saudi Arabia intervened in Yemen because of the Ansar Allah’s takeover

Of course, there’s no doubting that this narrative is 100% completely unequivocally true…Never mind the fact that after the war had already begun, US National Security Council spokesperson Bernadette Meehan said that the US’ security assessment was that Iran “does not exert command and control over the Houthis [i.e Ansar Allah] in Yemen.” 
 
And also, please disregard assessments by US intelligence officials that challenged the narrative that Iran is exerting control in Yemen on the Ansar Allah movement while you’re at it.

Now that we’ve gotten the sarcasm out of the way let’s talk about what’s going on in Yemen: Saudi Arabia’s battle against an impoverished people who refuse decades-old Saudi interference in their own affairs.
 
Going into the war, Saudi Arabia also chose to drag a number of countries along with it, including the UAE, who has also played a major role during the war. The idea was to create a sort of “Arab” or regional consensus against Yemen. The rationale was also clear: they're poor, they wear sandals, and they have a few machine guns, what harm can they can do? 

The recent targeting of the UAE, specifically Abu Dhabi, for the first and second time by the Yemeni armed forces by drones and ballistic missiles, has raised a number of questions regarding the UAE’s role during the war, and why the Ansar Allah chose to target it now after more than 7 years of war.

Why did the UAE join the Saudi-led war on Yemen?

Aside from the fact that there is a personal dimension to the relationship between Mohammad bin Salman and Mohammad bin Zayed, Crown Princes of Saudi Arabia and UAE respectively,  the Emiratis did not go into the war for free. They involved themselves in the war effort with expectations of fulfilling their own interests, which differed from the Saudis'. 

Both powers have had different strategies and goals since entering the war; While the Saudis aspired to topple the Ansar Allah and bring the resigned Abdrabbuh Mansur Hadi back into power as president in order to secure their interests, while the Emiratis sought to weaken the Ansar Allah by gaining influence in Yemen's coastal areas, particularly in the south. That way, they would be able to secure their influence on shipping lanes around the Bab-el-Mandeb straight up to the Horn of Africa.

The Saudis and Emiratis also backed different actors in order to achieve these goals. While the Saudis backed pro-Hadi forces and the Islah party, trying to play the "legitimacy" angle, the UAE considered Hadi to be incompetent, and thus backed southern Yemeni fighters in order to weaken the Ansar Allah, but ended up clashing with the Saudis down the line when the differences between the different factions ended up creating battles for influence.

Where they held power

The main presence of the UAE-backed forces lies in Aden, which Hadi had proclaimed to be the temporary and economic capital of Yemen until Sanaa is reclaimed. Though a small country, the Emirates had been trying to assert its military presence in Yemen by way of its advanced equipment and advanced training.

In 2017, the Emiratis were planning to retake the port city of Al-Hudaydah. However, as the war dragged on, they began to reach a stalemate, and in 2019 the UAE decided to change its approach towards the war on Yemen, and withdraw. 

This was completely baffling for the Saudis, who were trying to convince the UAE to remain in the war, however, the Emirates was experiencing an economic slowdown at the time, and could not handle the burden of a battle of attrition. Moreover, Saudi Arabia would still accommodate it in terms of access to Yemeni naval facilities, thereby allowing it to keep some control over maritime lanes from the Indian Ocean to the Mediterranean.

There was also the matter of securing their backs. It seems that an unwritten agreement had been arrived to at the time (according to Abdul-Bari Atwan) between the UAE and the Ansar Allah that stipulated that the UAE would no longer interfere in matters of the North (i.e Ansar Allah territories), and that it would handle its own matters in the South where the separatists are in control.

So why was the UAE targeted?

Marib was about to be liberated.

Marib isn't just an important win for the Ansar Allah because of its position. The city is effectively the last bastion of pro-coalition forces, and where they're likely to put up the fiercest fight. The very fact that the Marib basin is Yemen's most important oil and gas basin would allow the Ansar Allah significant leverage in any negotiations, and tip the balance of power in their favor.

As reports started pouring in early in December that Marib was a few days away from being liberated, the Yemeni armed forces seized an Emirati military cargo ship, and released footage that showed that the ship contained military equipment that the UAE had dispatched to allied forces.

This, for the Ansar Allah, was the first instance of the Emirates' violation of the agreement, and of their return to direct interference in the war, as this equipment was meant to bolster troop presence, equipment, and mobilization in Marib and Shabwa.

The second, more serious instance, was UAE support for the Giants Brigade, and the brigades' relocation from operations in the South, specifically Bab-el-Mandeb, to support the Saudi-led coalition forces in Shabwa and Marib, lest the region should fall into the hands of the Ansar Allah. 

The UAE has long prided itself on being an oasis of investment and security, which in a few decades' time was transformed from a desert into a testament of advancement. The problem is that capital is cowardly and fleeting, and will run away at a sign of instability.

The UAE is not Saudi Arabia. Saudi Arabia is a large country that has the capacity to absorb attacks made by the Ansar Allah without being completely destabilized. The UAE does not have that capacity. Though it was able to brush off the attacks made this month, it would not be able to sustain continued attacks made on its cities, as they would be enough to change the Emirates' image of being the secure country that it is.

Moreso, these two attacks were only messages. They both targeted Abu Dhabi using controlled, precision strikes against the energy infrastructure, using drones and ballistic missiles that traveled upwards of 1100 km without being detected. The Emirates is vulnerable is what the attacks meant, and though Abu Dhabi was the target now, Dubai might be next.

Giants Brigade relocated

It seems the UAE received the Ansar Allah's message, as the Giants Brigade began relocating just yesterday on the 28th. However, to what extent this will be reflected on Marib remains to be seen. 

The Emirates has already been targeted twice, and the Ansar Allah will not shy away from targeting it again if it decides to pursue a course of direct interference in the war.