THE DISPUTE between the Islamic State and Al Qaeda is more than just a fight for power within the jihadist movement. The two organizations differ fundamentally on whom they see as their main enemy, which strategies and tactics to use in attacking that enemy, and which social issues and other concerns to emphasize.

Although the ultimate goal of Al Qaeda is to overthrow the corrupt “apostate” regimes in the Middle East and replace them with “true” Islamic governments, Al Qaeda’s primary enemy is the United States, which it sees as the root cause of the Middle East’s problems. The logic behind this “far enemy” strategy is based on the idea that U.S. military and economic support for corrupt dictators in the Middle East—such as the leaders of Egypt and Saudi Arabia—is what has enabled these regimes to withstand attempts by “the people” (namely, the jihadists) to overthrow them. By targeting the United States, Al Qaeda believes it will eventually force the United States to withdraw its support for these regimes and pull out of the region altogether, thus leaving the regimes vulnerable to attack from within.

Al Qaeda considers Shia Muslims to be apostates but sees killing sprees against them as too extreme and thus detrimental to the broader jihadist project. Zawahiri criticized AQI’s killing of Shia in private correspondence captured by U.S. forces (asking Zarqawi, “Why kill ordinary Shia considering that they are forgiven because of their ignorance?”) and argued that this was a distraction from targeting the Americans. Strategically, Al Qaeda believes that the “Muslim masses,” without whose support Al Qaeda will wither and die, do not really understand or particularly care about the doctrinal differences between Sunni and Shia, and when they see jihadists blowing up Shia mosques or slaughtering Shia civilians, all they see are Muslims killing other Muslims.

The Islamic State does not follow Al Qaeda’s “far enemy” strategy, preferring instead the “near enemy” strategy, albeit on a regional level. As such, the primary target of the Islamic State has not been the United States, but rather apostate regimes in the Arab world—namely, the Assad regime in Syria and the Abadi regime in Iraq. Like his predecessors in AQI, Baghdadi favors first purifying the Islamic community by attacking Shia and other religious minorities as well as rival jihadist groups. The Islamic State’s long list of enemies includes the Iraqi Shia, Hezbollah, the Yazidis (a Kurdish ethnoreligious minority located predominantly in Iraq), the wider Kurdish community in Iraq, the Kurds in Syria and rival opposition groups in Syria (including Jabhat al-Nusra).

In addition to this difference in focus, Al Qaeda believes in playing nice with others; the Islamic State does not. Jabhat al-Nusra, Zawahiri’s designated affiliate in Syria and the Islamic State’s rival, works with other Syrian fighters against the Assad regime and, by the low standards of the Syrian civil war, is relatively restrained in attacks on civilians—in fact, at the same time the Islamic State was making headlines for beheading captured Americans, Jabhat al-Nusra made headlines for releasing the UN peacekeepers it had captured. Having learned from AQI’s disaster in Iraq when the population turned against it, in areas Jabhat al-Nusra controls, it proselytizes rather than terrorizes to convince Muslims to embrace “true” Islam. When U.S. forces bombed Jabhat al-Nusra because of its links to Al Qaeda, many Syrians were outraged, believing America was striking a dedicated foe of the Assad regime.

Al Qaeda has long used a mix of strategies to achieve its objectives. To fight the United States, Al Qaeda plots terrorism “spectaculars” to electrify the Muslim world (and get Muslims to follow Al Qaeda’s banner) and to convince the United States to retreat from the Muslim world. The model is based on the U.S. withdrawals from Lebanon after Hezbollah bombed the Marine barracks and U.S. embassy there and the “Black Hawk Down” incident in Somalia. In addition, Al Qaeda supports insurgents that fight against U.S.-backed regimes (and U.S. forces in places like Afghanistan, where it hopes to replicate the Soviet experience). Finally, Al Qaeda issues a flood of propaganda to convince Muslims that jihad is their obligation and to convince jihadists to adopt Al Qaeda’s goals over their local ones.

The Islamic State embraces some of these goals, but even where there is agreement in principle, its approach is quite different. The Islamic State seeks to build, well, an Islamic state. So its strategy is to control territory, steadily consolidating and expanding its position. Part of this is ideological: it wants to create a government where Muslims can live under Islamic law (or the Islamic State’s twisted version of it). Part of this is inspirational: by creating an Islamic state, it excites many Muslims, who then embrace the group. And part of it is basic strategy: by controlling territory it can build an army, and by using its army it can control more territory.

Al Qaeda in theory supports a caliphate, but Zawahiri envisioned this as a long-term goal. Back in the day, although bin Laden and Zawahiri supported AQI publicly, in private they did not approve of its declaration of an Islamic state in Iraq. In particular, Zawahiri feared that AQI was putting the cart before the horse: you need full control over territory and popular support before proclaiming an Islamic state, not the other way around.

Al Qaeda has never shown much interest in taking or holding territory in order to set up an Islamic state and govern, despite the fact that doing so is one of its stated goals; on the contrary, the only reason it has ever shown interest in territory is as a safe haven and as a place to set up training camps. For example, although Al Qaeda declared the Taliban leader Mullah Muhammad Omar to be the caliph of the Islamic Emirate of Afghanistan, the Al Qaeda leadership never showed any interest in trying to become part of the governing apparatus of the Taliban. Rather, it used its safe haven in Taliban territory as a base from which to plan additional attacks against the United States and support other jihadists in their fights against area regimes.

The two groups’ preferred tactics reflect these strategic differences. Al Qaeda has long favored large-scale, dramatic attacks against strategic or symbolic targets. The attacks on the World Trade Center and the Pentagon on 9/11 are the most prominent, but the 1998 bombings of the U.S. embassies in Kenya and Tanzania, the attack on USS Cole in the Port of Aden in 2000 and plots like the 2005 attempt to down more than ten transatlantic flights all show an emphasis on the spectacular. At the same time, Al Qaeda has backed an array of smaller terrorist attacks on Western, Jewish and other enemy targets, trained insurgents and otherwise tried to build guerrilla armies.

Yet although Al Qaeda has repeatedly called for attacks against Westerners, and especially Americans, it has refrained from killing Westerners when it suited its purposes. The most notable example of this is Al Qaeda’s decision on multiple occasions to grant Western journalists safe passage into Al Qaeda safe havens and allow them to interview bin Laden face to face. Terrorism doesn’t work if no one is watching, and in the days before YouTube and Twitter, Al Qaeda needed journalists to bring its message to its target audience.

The Islamic State evolved out of the civil wars in Iraq and Syria, and its tactics reflect this context. The Islamic State seeks to conquer, and thus it deploys artillery, massed forces and even tanks as it sweeps into new areas or defends existing holdings. Terrorism, in this context, is part of revolutionary war: it is used to undermine morale in the army and police, force a sectarian backlash or otherwise create dynamics that help conquest on the ground. But it is an adjunct to a more conventional struggle.

In territory it controls, the Islamic State uses mass executions, public beheadings, rape and symbolic crucifixion displays to terrorize the population into submission and “purify” the community, and at the same time provides basic (if minimal) services. This mix earns them some support, or at least acquiescence, from the population. Al Qaeda, in contrast, favors a more measured approach. A decade ago Zawahiri chastised the Iraqi jihadists for their brutality, correctly believing this would turn the population against them and alienate the broader Muslim community, and he has raised this issue in the current conflict as well. Al Qaeda recommends proselytizing in the parts of Syria where its affiliate Jabhat al-Nusra holds sway, trying to convince local Muslims to adopt Al Qaeda’s views rather than forcing them to do so.

HELPING THE Islamic State’s meteoric rise and its ability to attract tens of thousands of young men (and a few women) to its ranks from around the world, including from many Western countries, is its ability to use social media to disseminate its propaganda to its target demographic: angsty Muslim males roughly between the ages of eighteen and thirty-five. The leaders and members of the Islamic State are a generation younger than those of Al Qaeda (Baghdadi is believed to be around forty-three years old, whereas Zawahiri is sixty-three years old), and the generation gap shows.