President Donald Trump is reportedly about to extend a terrorism designation to Iran’s Islamic Revolutionary Guard Corps (IRGC) in its entirety. The IRGC is both the dominant force inside Iran and the instrument through which the Islamic Republic projects power abroad. Operating throughout the region, the IRGC is deeply entrenched in Lebanon; the domain of Hezbollah.

For years, while acknowledging that Lebanese Hezbollah is backed and “inspired” by Iran, many policymakers and analysts have treated the group as an independent actor driven by its “resistance” to Israel and one that would not fight on behalf of Syria’s Bashar al Assad for fear of compromising its stature as the premier anti-Israel resistance group.

The Syrian war has shown otherwise. Revealing testimonies by key figures in the war effort have clarified the way in which Hezbollah—often thought of erroneously as a “proxy” —is actually at the heart of Iran’s command structure.

Last month, a Lebanese newspaper quoted Hezbollah leader Hassan Nasrallah, telling a public audience that he had traveled to Iran for a meeting with Supreme Leader Ali Khamenei to discuss the situation in Syria during the early stages of the war. “At the time, everyone was convinced the regime would fall in two or three months,” Nasrallah reportedly said in the pro-Hezbollah Al-Akhbar newspaper.

Nasrallah then put forward his view of the challenge in Syria. “If we don’t fight in Damascus, we will be forced to fight in Hermel, Baalbek, Dahiyeh, Ghaziyeh, the Western Bekaa, and South Lebanon,” he is said to have told Khamenei. According to the newspaper report, Khamenei supposedly agreed, adding that Iran would likewise be forced to fight on its soil “in Kerman, Khuzestan and Tehran.”

It is not clear when, precisely, Nasrallah’s meeting with Khamenei took place. The likely date is April 2013, when newspapers reported that Nasrallah made a quiet trip to Iran. A month later, the battle of Qusayr took place, marking Hezbollah’s full-blown intervention in Syria. Whether this is indeed the correct date of the meeting, the central place Hezbollah occupies in the Iranian leadership’s planning process and command and control structure is coming into view.

The picture becomes clearer when taking into account the recollections of a late Islamic Revolutionary Guard Corps (IRGC) general who played a key role in Iran’s war effort. Biographer Gol-Ali Babai’s detailed memoir of Hossein Hamedani, whom the IRGC posthumously promoted to Major General, was recently published (the second anniversary of his death near Aleppo is this week). According to Hamedani, in early January 2012, Qassem Soleimani, chief of the IRGC external operations branch known as the Quds Force, asked Hamedani to lead an advisory mission to Syria. By that time, it was apparent Assad’s forces were failing to put down the uprising against the regime.

Hamedani already had extensive experience in irregular warfare. Prior to 1979, he trained in the Shah’s Airborne special forces, then participated in crushing Kurdish separatists following the revolution. In the 1980’s, he led regular and irregular troops during the Iran-Iraq War before deploying for a year to the Congo as a military adviser in the mid-1990’s. More recently, he played a key role in the violent quelling of Iran’s 2009 mass protests.

Hamedani accepted the assignment Soleimani gave him. The first focus of Hamedani’s mission — tactical training for some 2,000 Alawites and 500 Shiites — was in Homs, near the Lebanese border, which is where Hezbollah’s intervention would begin as well.

Shortly thereafter, Hamedani drafts a strategy document for Syria. At this point in his account, Hamedani offers an interesting nugget. When he presented his plan to Soleimani, Hamedani says the Quds Force commander reviewed it and told him to seek Nasrallah’s counsel. It was the Supreme Leader’s instructions, Soleimani said, for all “comprehensive policies of the Resistance Axis in Syria to be under the supervision of Sayyed Hassan Nasrallah,” who “managed all issues related to Syria per [Khamenei’s] directives.” This episode suggests that Nasrallah is so integral to the Iranian command structure that the Supreme Leader assigns him a supervisory role in the Syrian theater, not just an advisory one.

In keeping with Soleimani’s guidance, Hamedani traveled to Beirut, where he met Nasrallah and discussed his plan with him and with “Aba Mahdi,” the Qouds Force commander in Lebanon (that is, Mohammad Reza Zahedi, a.k.a., Hassan Mahdavi). Hamedani presented a comprehensive military, security, political, economic and cultural strategy. He would publicize certain details of it before his death in 2015. It was essentially the template of the revolutionary model Iran has been exporting for decades. This included the creation of Syrian popular militias modeled after Iran’s Basij force, the establishment of a Syrian Hezbollah, and the entry of Iran’s construction arms into Syria.

Nasrallah’s advice at the time was to focus first on the military and security aspects, since the Syrian leadership “was drowning.”

“Right now, we have to drag them out of the swamp,” Nasrallah reportedly told Hamedani. according to the memoir.  “This is the first, and most important strategic step.”

To be sure, memoirs of Iranian revolutionary commanders should always be read with a grain of salt. The same applies to the rather hagiographic account of Nasrallah’s comments,  as reported in the Hezbollah-friendly Al-Akhbar. Nevertheless, an instructive picture emerges from these accounts of Tehran’s strategic planning process, the Iranian command structure, and Hezbollah’s place in it.

At the top sits the Supreme Leader, Ali Khamenei, who has final say on policy. Second in command, is Quds Force chief Qassem Soleimani, the person who oversees the regional strategy and the vast network of Iranian-led forces. Answering to Soleimani are handpicked senior generals, like Hamedani, who are tasked with specific missions. Nasrallah’s position is near this tier. As the commander of Iran’s Lebanese outpost, Nasrallah advises Hamedani, and at some point is summoned to Tehran to meet with Khamenei and Soleimani. Like a Quds Force commander, he presents a situation report and Khamenei gives him a commission (taklif) to have Hezbollah intervene directly.

Hezbollah is often described as an “ally” or “partner” of Iran. This language reflects the view of Hezbollah as primarily a Lebanese actor, pursuing a separate agenda and strategy. New evidence shows why this view should be reconsidered. Hezbollah – like the IRGC-Quds Force – is an integral component of the Islamic Republic’s command structure.

Consequently, as the U.S. has signaled a muscular approach toward Iran, a proper understanding of the Hezbollah-Iran relationship will allow the U.S. to view Hezbollah as a special branch of the Guard Corps.