left the same year to revitalize the resistance and founded the Patriotic Union of Kurdistan. This event created the baseline for the political discontent between the KDP and PUK that to this day divides Peshmerga forces and much of Kurdish society in Kurdistan. After Mustafa Barzani's death in 1979, his son Masoud Barzani took his position. As tension increased between KDP and PUK, most Peshmerga fought to keep a region under their own party's control while also fighting off Iraqi Army incursions. Following the First Persian Gulf War, Iraqi Kurdistan saw the Kurdish Civil War between the two major parties, the KDP and the PUK, and Peshmerga forces were used to fight each other. The civil war officially ended in September 1998 when Barzani and Talabani signed the Washington Agreement establishing a formal peace treaty. In the agreement, the parties agreed to share revenue and power, deny the use of northern Iraq to the Kurdistan Workers' Party (PKK), and not allow Iraqi troops into the Kurdish regions. By then, around 5,000 had been killed on both sides, and many more had been evicted for being on the wrong side. In the years after, tension remained high, but both parties moved towards each other, and in 2003 they both took part in the overthrowing of the Baathist regime as part of the Iraq War. Unlike other militia forces, the Peshmerga were never prohibited by Iraqi law. In 2014, the Peshmerga withdrew from the Nineveh Plains which was said by the locals as being a contributing factor of the quick Islamic State victory in the invasion, and the widespread massacre of Yazidis, who were rendered defenseless. Structure and capabilities The Peshmerga are mostly divided among forces loyal to the Kurdistan Democratic Party (KDP) and those loyal to the Patriotic Union of Kurdistan (PUK), while other, minor Kurdish parties such as the Kurdistan Socialist Democratic Party also have their own small Peshmerga units. The KDP and PUK do not disclose information about the composition of their forces with government or media. Thus there is no reliable number of how many Peshmerga fighters exist. Media outlets have speculated that there are between 150,000 and 200,000 Peshmerga, but this number is highly disputed. Peshmerga have divided Kurdistan Region into a KDP-governed "yellow" zone covering Dohuk Governorate and Erbil Governorate and a PUK-governed "green" zone covering Sulaymaniyah Governorate and Halabja Governorate. Each zone has its own