Reupping my detailed @ctcwp piece on evolving Houthi military capabilities, driven by my field research & coverage of Houthi mil ops stretching back to the six wars, pre-2011). The evidence suggests that IRGC/Leb Hezb advise/assist drove the transformation https://ctc.usma.edu/houthi-war-machine-guerrilla-war-state-capture/

The Houthis are undeniably good at tribal coalition building and breaking, though even this benefited from Leb Hezb advise/assist, partic in collating large intel datasets on key leaders & communities. Regards Houthi strike capabilities, this quickly became a pure IRGC test-bed.

The fighting on the northern border with Saudi was driven partly by traditional Houthi fighting skills seen in the six wars, but GREATLY improved by intensive advise/assist from Leb Hezb, reflecting their own experience of very similar south Lebanon border operations.

Houthi use of the Explosively Formed Penetrator - uniquely dense employment, even compared to south Lebanon and Sadr City perimeter, 2008 - was Leb Hezb-driven, IRFGC-supplied. Similar with ATGM heavy sniping and use of Iranian anti-materiel rifles.

Anti-shipping warfare by the Houthis was driven by Leb Hezb and IRGC advisor and maintenance cells, incl introduction of C-802 (much as Iran introduced it to LH), introduction of drone boat control suites (proven as made in Tehran), and combat diver training by Leb Hezb.

Strike capability is an imported IRGC capability, including direct provision of whole systems (Qiam MRBM from Iran); IRGC-executed conversion of local Scud & SA-2 systems using Iranian designs; local manufacture of tweaked Iranian drone designs (Abadil T & many others).

What matters to me is that US govt knows all of this as proven fact, right down to the last skeptic.

I personally took a lot of convincing about IRGC penetration 2009-2014, but the evidence is overwhelming & getting richer by the day.

To conclude, IRGC funds & technical assistance never comes for free. It is a lever of control. NO-ONE ever starts with the intent of becoming a proxy, but that's how most (not all) end up. Look to the fissures in the Houthi leadership for the cracks IRGC is exploiting.

This was a very important part of the story for me, and well documented -- Iran/LH provision of military advice and aid to the Houthis from 2009 onwards, not 2014 onwards. IRGC had a project in Houthi-stan since the 80s but it went into military overdrive from 2009.

One important factor that is often overlooked is that Houthi distrust (justified) of former Salih military people resulted in the Houthis going further with IRGC/LH than many might have expected of this xenophobic group.