Hezbollah has a long and not well-known history dating back to the Lebanese civil war. Iran has funded and used this organization for a long time. Here is news that they are trying to establish greater numbers of Hezbollah in Iraq.

Inside the plot by Iran’s Soleimani to attack U.S. forces in Iraq

https://www.reuters.com/article/us-iraq-security-soleimani-insight-idUSKBN1Z301Z

Should you want a little more backstory, the below article is about Project Cassandra. The Cassandra project was established under George W. Bush after 9/11 to gather intelligence about threats coming from the middle east. The Obama administration let the Cassandra project wither due to a lack of funding once the administration found out they were delving into Hezbollah and Iran.

https://www.politico.com/interactives/2017/obama-hezbollah-drug-trafficking-investigation/?fbclid=IwAR0k52RuZHPZRbTHcaKfT-uUcEqfDpeLtppC95gtOv8LARWA8ss_PRLJb2k