The city of Aleppo in northern Syria was the scene of fierce clashes between Syrian army forces and fighters with Hizbullah, the Lebanese Shia militia, last week. The fighting between the ostensible allies left dozens of Hizbullah fighters dead and exposed major differences between the two sides. Both sides used artillery, mortars and heavy machine guns in the clashes. As the battle spread to other towns hosting fighters from both parties, Iraqi Shia militias supported Hizbullah forces against Syrian regime fighters, while the Syrian air force intervened to provide air support for regime forces and shell Hizbullah positions. The clashes erupted following an operation carried out by Division 13 of the opposition Free Syrian Army (FSA), which infiltrated areas held by the Syrian army and regime militias and killed 10 Hizbullah fighters. Hizbullah then accused Syrian army units of failing its fighters in battle, conspiring with the opposition, and leaving them vulnerable to the FSA. The arguments escalated into a firefight with light weapons, and Hizbullah fighters killed a high-ranking Syrian officer along with six soldiers in retaliation for the deaths. The clashes then spread to the towns of Nabbal and Al-Zahra, inhabited mostly by Shias and protected by joint Hizbullah-regime forces. Hizbullah forces then attacked more Syrian army soldiers, after which both sides took up heavy weapons before military planes were called in. Officials close to the regime led by Syrian President Bashar Al-Assad sent a message to Hizbullah, telling the group that the auxiliary forces supporting the Syrian army “should realise that they are there to protect Syria, not to extend their own control.” They urged the forces to remember that “the army of the regime supported Hizbullah in its war with Israel in 2006” and cautioned them against “toying with the regime”. Although regime loyalists generally prevent criticisms of Hizbullah in Syria, Syrian army officers and soldiers have complained of how they are treated by Hizbullah fighters, saying that they make them feel they “are under Hizbullah's authority,” as one of the soldiers put it. Hundreds of checkpoints manned by Hizbullah in Syria stop all Syrians indiscriminately, whether they are regime opponents or supporters. Hizbullah also controls large areas of western Syria, adjacent to Lebanon, that the Syrian army is only permitted to enter with the approval of the Lebanese group. Disputes between the allied forces in Syria have been festering along two primary lines, the first between the regime and Hizbullah. This week's clashes occurred in a climate where the pro-Iranian Hizbullah is increasingly wary of Russian support for the regime and the regime is attempting to reduce Hizbullah's presence. The pro-regime Alawite community in Syria is also concerned about the growing influence of Hizbullah and for the first time has criticised Iran's attempts to spread Shiism in Alawite areas. Differences are also apparent between the regime and Russia. Moscow recently declared a ceasefire in Aleppo, despite the wishes of the regime, which wanted Russian forces supported by Iranian and Lebanese units to advance the battle lines. The Al-Assad regime thus accused its Russian ally of impeding advances in Aleppo, and this culminated in a surprise meeting between Al-Assad and the Russian defence minister at the Russian Hmeimim military base on the Syrian coast. Al-Assad attended the meeting alone, and photographs of the meeting suggested that the Russian minister was cross-examining, rather than talking with, Al-Assad. “The dispute between the regime and Hizbullah began to grow as Hizbullah extended its influence in Damascus,” according to Osama Abu Zeid, an advisor to the opposition FSA. “Hizbullah staged Ashoura processions and put its hands on the Hamidiya Market, the Umayyad Mosque, and the Hariqa area, which are closed areas subject to strict security measures as they are home to Shia tombs.” He added, “The dispute was exacerbated by bombings in the area of Sayyeda Zeinab two weeks ago, which killed dozens of Shias loyal to Hizbullah and Iran.” The area of the bombings is fortified by Syrian regime militias and would be difficult for the opposition to penetrate. Last month, Hizbullah military commander Mustafa Badr Al-Din was killed in the movement's headquarters near Damascus International Airport. Fellow Hizbullah commander Emad Mughniyeh met the same fate a year and a half ago. In the intervening period many Hizbullah officers have been killed by friendly fire, leading some media outlets to conclude that Syria has become “a graveyard” for Hizbullah leaders. After years of fighting side by side, trust between regime forces and Hizbullah militias has been shaken. The regime militias are often highly partisan Alawites who insist on the perpetuation of Al-Assad family rule in Syria. In contrast, Hizbullah have Shia loyalties, favour Iranian nationalist slogans, and care less about Al-Assad personally than about implementing Tehran's projects in the region. Theoretically, there is an alliance between the Syrian regime militias and the Lebanese Hizbullah forces, but in practice the two parties are often at odds. Hizbullah militias erode the influence and tight security grip of regime forces and seek to cement the Iranian influence in Syria, turning Hizbullah-held areas into islands outside the control of the Syrian regime. Valerie Petitpierre, Syria coordinator for the International Committee of the Red Cross, told Al-Ahram Weekly before her arrival in Damascus last month that the Red Cross has received approval from the Syrian authorities to bring assistance into the city of Dariya near Damascus. But while the aid convoys passed through regime checkpoints, a Hizbullah checkpoint under the control of Iranian officers refused them passage and forced them to return. This is one example of how Hizbullah flaunts the authority of the Syrian regime. In this tense relationship, nothing stands in the way of Hizbullah but the Syrian opposition fighters. Neither the regime nor the Kurdish separatists, nor even the Islamic State (IS) group, is greatly concerned with Hizbullah's expansion or engaging it in battle. “Syria would never accept the idea of being geographically divided, and it no longer accepts divided authority,” said Syrian dissident Fawaz Tello. “The conflict in Syria cannot lead to a compromise or power sharing after all the sectarian crimes. The conflict was chosen by the regime and its sectarian supporters, and it is the basis on which we're waging our revolution today.” He added, “It's no longer about simply changing a sectarian regime. Today we're waging a revolution in defence of our existence in the face of sectarian foreigners who have infiltrated and taken over parts of Syria. This is a revolution for our very existence, and we'll lose everything if we don't win.” Iran is striving to be accepted as a major party in the negotiations on the Syrian crisis, fearing a deal between the regime and Russia. It has tried to forestall the latter possibility by taking military control of strategic areas using the Iranian Revolutionary Guards, Hizbullah fighters, and Iraqi and Afghan sectarian militias, betting on a broad group of militias loyal to its doctrine of the guardianship of the jurisprudent in Iran. Since Hizbullah joined the Syrian conflict on the side of the regime, it has linked its fate to that of the regime. But there is no indication that the alliance will allow it to emerge victorious, and this will determine Hizbullah's political future in Lebanon and the wider region.