https://nationalinterest.org/blog/buzz/behold-irans-mini-submarine-force-dangerous-partly-thanks-north-korea-59562

The National Interest previously looked at this nuanced question with overviews of Iran’s air force and surface navy. We now turn to what is arguably the core of Iran’s conventional military strength, and the reason why it boasts the fourth-strongest navy in the world: its submarine force.

Perhaps the most striking aspect of Iran’s submarine roster is its sheer size, especially in relation to the rest of its navy. Whereas Iran’s combined output of operational corvettes, frigates, and destroyers hardly exceeds 10, it currently fields a whopping 34 submarines. The vast majority of these are midget-class–or “littoral”–diesel-electric vessels, with roughly two dozen from Iran’s homemade Ghadir class and several more from the North Korean Yugo class. Impressively, the Ghadir is much smaller but still has strong offensive capabilities; Ghadir vessels boast the same 533 mm torpedo tubes as the handful of Iran’s much larger Kilo vessels, only fewer at two versus six.

https://csbaonline.org/uploads/documents/CSBA_SWA_FNL-WEB.pdf

From the article above, we really do need to update our military doctrine

Should the United States choose to intervene in spite of Iran’s A2/AD capabilities, Iran would likely hope to inflict significant losses on U.S. forward-deployed forces at the outset of a conflict while preventing the U.S. military from reinforcing those forces by sea and air. This may help create the time and space needed for Iran to consolidate its gains and force the United States to choose between fighting its way into the Persian Gulf at great cost and with little or no support from regional states, or accepting a new regional balance of power that favors Iran. Tehran may hope that the United States, faced with the prospect of a long and costly campaign to reopen the Gulf, may ultimately balk at defending autocratic Gulf regimes that have never been particularly popular with the American public

The difficult acoustic conditions in the Persian Gulf and its approaches complicate anti-submarine warfare (ASW) operations;

https://thefederalist.com/2019/05/24/irans-cash-crunch-isnt-disabling-hezbollah-yet/

Iran’s global battering ram, the U.S.-designated terrorist group Lebanese Hezbollah, has entered such dire financial straits that it can no longer supply free groceries to its employees and beseeches the people to fill donation boxes. So said The Washington Post in a May 18 story, which squared with a March 28 story in The New York Times. Both papers report tough times for the terror group

Left unsaid by both the Post and the Times is that Hezbollah achieved significant financial autonomy from Iran more than a decade ago. How? Starting in about 2006, it moved into Latin America and hit it very big in the international cocaine trafficking industry.

Some Hezbollah experts suggest the organization hit it so big as a global drug trafficker that its profits began to exceed what Iran gives in recent years.

The DEA’s 2008 to 2016 “Project Cassandra” found that Hezbollah’s “External Security Organization Business Affairs” arm collected $1 billion a year from money laundering, criminal activities, and drug and weapons trade. All through the Obama years and into the Trump years, Hezbollah and South American drug cartels have been involved in cocaine shipments from Latin America to West Africa to European markets, as well as through Venezuela and Mexico to the United States.

None of this is mentioned in either the Times or the Post, even though a discussion seemed more than prompted when a senior Hezbollah official was quoted saying, “Hezbollah has other sources of income and plans to aggressively seek out more, hoping to ‘turn this threat into an opportunity to develop new revenue streams.’”

https://www.politico.eu/article/obama-hezbollah-the-secret-backstory-of-how-let-off-the-hook/

In its determination to secure a nuclear deal with Iran, the Obama administration derailed an ambitious law enforcement campaign targeting drug trafficking by the Iranian-backed terrorist group Hezbollah, even as it was funneling cocaine into the United States, according to a POLITICO investigation.

The campaign, dubbed Project Cassandra, was launched in 2008 after the Drug Enforcement Administration amassed evidence that Hezbollah had transformed itself from a Middle East-focused military and political organization into an international crime syndicate that some investigators believed was collecting $1 billion a year from drug and weapons trafficking, money laundering and other criminal activities.