A year after declaring his caliphate, it is clear that the secret of Abu Bakr al-Baghdadi’s success is the army and state he has built from the remnants of Saddam Hussein’s military, and the allegiance he has won or coerced from alienated Sunni Muslims in Iraq, Syria, and beyond.

In that year, the self-appointed caliph has expanded his turf from eastern Syria and western Iraq to include adherents in pockets of war-racked Libya and Egypt’s lawless Sinai Peninsula.

He has set his sights on Saudi Arabia, birthplace of Islam, and his Islamic State has launched an online magazine for Turks, who have volunteered for his jihad in the hundreds if not thousands.

His speeches, freighted with Quranic verses ripped from their context and loaded with hadith — sayings attributed to the prophet, many of them regarded as spurious — sound more like sermons.

The recruiting drum he beats is loud and clear, summoning his followers to a pitiless jihad against Shiite heretics, Christian crusaders, Jewish infidels, and Kurdish atheists. He berates Arab despots for defiling the honor of Sunni Islam.

His message is this: Where Iraq’s rulers could not prevent the 2003 U.S.-led invasion that delivered the country into the hands of Shiites, and were unwilling to mount a jihad against Alawite minority rule in Syria, much less deliver Jerusalem from Israel, the Islamic State group will now lead the way.

In this pseudo-religious and sectarian narrative, Islamic State jihadis are on a divine mission to redeem a fallen Arab world by fire and the sword — as shown in its videos of beheadings and immolations.

Other factors are critical to the group’s success. Beyond the alliance of Saddam loyalists and Islamist extremists born of the Iraq war, al-Baghdadi relies on local Sunnis and their tribes, whereas his jihadi precursors relied more on foreign fighters.

Despite thousands of foreign volunteers, jihadi ideologues say Islamic State forces are 90 percent Iraqi and 70 percent Syrian in its two main strongholds, where they have about 40,000 fighters and 60,000 supporters.

Al-Baghdadi, who forged links with Saddam’s Ba’athists while a prisoner during the U.S. occupation, also claims descent from the Prophet Muhammad and his Quraishi tribe — a heritage that allows him to assert that “we are the soldiers of the mission declared by the prophet.”

Abu Mohammad al-Maqdisi, the jihadi theorist who was the spiritual mentor of Abu Mussab al-Zarqawi, the Jordanian leader of al-Qaida in Iraq who was killed by an American airstrike in 2006, says that before it took over swaths of Syria and Iraq, Islamic State wiped out almost all other Islamist and Sunni rivals.

It gave them the choice of death or repentance, and declared war on its al-Qaida-allied rival in Syria, the Nusra Front.

“They now consider the Nusra Front apostates,” al-Maqdisi says in an online publication. Al-Baghdadi “is Iraqi, has a popular base in Iraq (and) he has Iraqi tribes with allegiance to him, while Abu Mussab (al-Zarqawi) was Jordanian and surrounded by foreign fighters.”

“They are winning militarily because they are depending on former Ba’athist officers who know their ground,” al-Maqdisi says.

But in the end they rely on fear.

Abu Qatada al-Filistini, another al-Qaida-linked ideologue who with al-Maqdisi has signed a fatwa declaring it legitimate to fight Islamic State, said, “this state is advancing because of the military, security and intelligence background of its leadership which seeks to impose a state of terror. They impose their authority, with blood, with the sword.”

The former al-Qaida godfathers — al-Maqdisi, who had ties to Osama bin Laden successor Ayman al-Zawahri, and Abu Qatada, deported from London to face terrorism charges in Jordan after a long court battle — see differences and similarities between Islamic State and al-Qaida, the movement al-Baghdadi has now eclipsed.

Unlike al-Qaida, which only established a tenuous ’emirate’ under the U.S. occupation before it was driven out of Anbar province, Islamic State is putting down roots. But Abu Qatada argues that it may contain the seeds of its own destruction.

“They are Ba’athist in the dictatorial and security sense,” he says in an online publication. “Their conflict with other Islamist groups including Nusra is bigger than their conflict with Hashd al-Shaabi,” Iraq’s Shiite militia coalition.

In his speech released on May 14 after unconfirmed reports he had been badly wounded in a U.S. airstrike, al-Baghdadi says; “Islam was never for a day the religion of peace; Islam is the religion of war.”

His followers’ assaults on the Shiites and their allies in Iraq will “make the Crusaders bleed and strengthen the pillars of the Caliphate,” and defeat Syrian Alawites and the Shiite Houthis in Yemen.

While this may sound like empty bombast to outsiders, for al-Baghdadi’s audience the point is that the Sunni army of Islamic State has often succeeded in kicking Shiites out of Sunni cities. Yet the very success of Islamic State suggests limits to its expansion.

The movement has gained footholds in ungoverned spaces such as Libya and the Sinai — and in territory from Nigeria to the Caucasus.

It is also adept at exploiting sectarian opportunities: the recent bombings of Shiite mosques in Saudi Arabia are an attempt to widen rifts between the kingdom’s Sunni majority and a marginalized Shiite minority.

But in the core of the caliphate, gains have so far been confined to Sunni areas. Attempts to break into Kurdish or Shiite territory have been beaten back.

Yet Islamic State is well implanted in its Syrian and Iraqi domains until the Sunnis can be persuaded to uproot them. That will not happen while they fear oppression from Baghdad and Damascus more than the brutality of the caliphate.

Islamic State ruthlessness is methodical. Taught by their Ba’athist commanders, they are a fast and flexible military force. But by the time they move on a Sunni city Islamic State will mostly have cleansed it of opponents who refuse to recant, and wiped out Islamist rivals.

They are also quick to seize local resources, from energy to bakeries and taxation, both to finance their operations and make themselves the source of patronage and jobs.

They have grown rich from selling oil, trading hostages and selling smuggled antiquities, says Hisham al-Hashemi, an Iraqi researcher on Islamic State. The group’s wealth is estimated at $8 billion to $9 billion, al-Hashemi says.

They have some administrative stability. Behind al-Baghdadi lies a leadership of depth and structure, and al-Baghdadi could easily be replaced.

Al-Baghdadi, who has a Ph.D. from the Islamic University of Baghdad on Islamic history, has an advisory council of nine members and about 23 emirs in charge of Sunni areas. They run their own ministries.

Underneath all this is a detailed governance structure that from Nineveh, the province of which Mosul is the capital, to the cities of Anbar is mostly run by ex-Ba’athist army officers who were nearly all U.S. prisoners in Camp Bucca jail, which became a sort of Islamic State university.