Yemen has no future sadly, other than being a militant playground for nations to leverage. The blame lies on everyone:
1. Ex-Yemeni corrupt government
2. Houthi's
3. Saudi-led Coalition
4. Iran
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Iran wanted to use Houthi's as means to ease pressure off regime in Syria back when the Syrian opposition was making progress, prior to Russian intervention. Houthi's had embarked on a risky campaign to take over the Yemeni capital, Sanaa. They succeeded, and the Saudi's worried that those efforts will be directed further south. A supposed ISIS bombing hit Houthi's mosques killing over a 100 people, that caused the Houthi's and ex-Yemeni government army members to conquer much of the west/southern provinces of Yemen. Which meant Saudi's had no other choice to intervene militarily, otherwise risk all of Western Yemen to the Houthi-led Alliance. That would allow Iran to build up military assets in that region for future blackmailing or threats against Saudi Arabia.
So the Saudi led campaign began with the usual infrastructure targeting, while scrambling to organize force on the ground as they were in a rush. UAE also played a role here, but was skeptical of what this force should entail, as it did' want the Yemeni Muslim Brotherhood to gain any influence. All while supporters of the Brotherhood in Yemen were upset that the organization was being very passive in its approach. Leading some of them to rethink their allegiances, and some subscribed to AQAP or ISIS agenda. Once this pro-Hadi force was formed, it seemed there were internal disputes.
And you see almost a weekly if not daily basis of bombings targeting Yemeni officials(pro-Saudi coalition) in Aden. All of these have been attributed to ISIS, although I would suggest otherwise. Maybe some of them are genuinely committed by ISIS, others have to be internal disputes or disputes between Saudi Arabia, UAE and Qatar. Then you have the Taiz Offensive which has not heeded results. Some rumors state this is because it will strengthen the Muslim Brotherhood, and therefore the coalition doesn't want to overly support them.
Regarding the current state, the Houthi-led Alliance is able to hold ground in major cities they control that matter to them in the north, northwest, and midwest of Yemen. The Saudi led forces are conducting offensives as well, but AQAP and ISIS seem to follow them everywhere they go. AQAP controls a lot of small towns to the East, and is also fighting for Aden, while ISIS is low-key but conducting assassinations and bombings. It seems that to the people of Yemen, none of the parties appeal to them. And some may choose the lesser 'evil', by 'less evil', I don't mean a group they consider least hardline. I mean groups that are least corrupt and appear independent.
Which is why I see AQAP and ISIS will be difficult to subdue in Yemen, but the Houthi-led and Saudi-led alliances will be more distracted by each other and their personal interests, and allow AQAP and ISIS to have larger presence. If the rate of the conflict remains as it is. It is almost now a race for territory, and I don't believe any party will utterly overcome the other. Only AQAP and ISIS will benefit from chaos, unless the other parties put forth proper solution or alternative for the people. They will however be stubborn.
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The camps of the region and overseas need to take a step back, stop plotting in dangerous manners, as they are making life miserable for everyone while giving hardline groups credibility.