. Al-Jawlani issued a statement denying the merger and complaining that neither he nor anyone else in al-Nusra's leadership had been consulted about it. In June 2013, Al Jazeera reported that it had obtained a letter written by al-Qaeda leader Ayman al-Zawahiri, addressed to both leaders, in which he ruled against the merger, and appointed an emissary to oversee relations between them to put an end to tensions. In the same month, al-Baghdadi released an audio message rejecting al-Zawahiri's ruling and declaring that the merger was going ahead. In October 2013, al-Zawahiri ordered the disbanding of ISIS, putting al-Nusra Front in charge of jihadist efforts in Syria, but al-Baghdadi contested al-Zawahiri's ruling on the basis of Islamic jurisprudence, and the group continued to operate in Syria. In February 2014, after an eight-month power struggle, al-Qaeda disavowed any relations with ISIS.
According to journalist Sarah Birke, there are "significant differences" between al-Nusra Front and ISIS. While al-Nusra actively calls for the overthrow of the Assad government, ISIS "tends to be more focused on establishing its own rule on conquered territory". ISIS is "far more ruthless" in building an Islamic state, "carrying out sectarian attacks and imposing sharia law immediately". While al-Nusra has a "large contingent of foreign fighters", it is seen as a home-grown group by many Syrians; by contrast, ISIS fighters have been described as "foreign 'occupiers'" by many Syrian refugees. It has a strong presence in central and northern Syria, where it has instituted sharia in a number of towns. The group reportedly controlled the four border towns of Atmeh, al-Bab, Azaz and Jarablus, allowing it to control the entrance and exit from Syria into Turkey. Foreign fighters in Syria include Russian-speaking jihadists who were part of Jaish al-Muhajireen wal-Ansar (JMA). In November 2013, the JMA's ethnic Chechen leader Abu Omar al-Shishani swore an oath of allegiance to al-Baghdadi; the group then split between those who followed al-Shishani in joining ISIS and those who continued to operate independently in the JMA under a new leadership.
In May 2014, al-Qaeda leader Ayman al-Zawahiri ordered al-Nusra Front to stop attacks on its rival ISIS. In June 2014, after continued fighting between the two groups, al-Nusra's branch in the Syrian town of al-Bukamal pledged allegiance to ISIS.
In January 2014, The Daily Telegraph said that Western intelligence sources believed that the Syrian government had made secret oil deals with ISIS and al-Nusra Front, saying that the militants were funding their campaign by selling crude oil to the regime from the oilfields which they had captured.
The Syrian government did not begin to fight ISIS until June 2014, despite it having had a presence in Syria since April 2013, according to Kurdish officials.
As Islamic State (2014–present)
On 29 June 2014, ISIS removed "Iraq and the Levant" from its name and began to refer to itself as the Islamic State, declaring the territory under its control a new caliphate and naming Abu Bakr al-Baghdadi as its caliph. On the first night of Ramadan, Shaykh Abu Muhammad al-Adnani al-Shami, spokesperson for ISIS, described the establishment of the caliphate as "a dream that lives in the depths of every Muslim believer" and "the abandoned obligation of the era". He said that the group's ruling Shura Council had decided to establish the caliphate formally and that Muslims around the world should now pledge their allegiance to the new caliph. The declaration of a caliphate has been criticized and ridiculed by Muslim scholars and rival Islamists inside and outside the occupied territory.
By that time, many moderate rebels had been assimilated into the group. In August 2014, a high-level IS commander said, "In the East of Syria, there is no Free Syrian Army any longer. All Free Syrian Army people [there] have joined the Islamic State". The Syrian Observatory for Human Rights claimed that the Islamic State recruited more than 6,300 fighters in July 2014 alone, many of them coming 