In this Sunday, June 21, 2015 photo, a defaced barrier with the Islamic State group's flag is toppled near the entrance to one of Saddam Hussein's damaged palaces in Tikrit, 80 miles (130 kilometers) north of Baghdad, Iraq. Civilians are trickling back into Saddam Hussein’s hometown as they look to start anew, the consequences of a year under Islamic State rule conspicuously written on its charred buildings and damaged homes.(AP Photo/ Hadi Mizban) Source: AP

Buoyed by a string of battlefield successes, the Kurds are waging an offensive through northern Syria.

The capture of the strategic town of Ein Issa - hours after the Kurdish troops took the nearby Brigade 93 military base - further squeezes the IS extremists, especially after they lost a major international supply line when the Kurds captured the town of Tal Abyad on the Turkish border last week.

The advance put the Kurdish fighters within about 50 kilometers of the Islamic State’s stronghold of Raqqa. But even with the aid of US-led airstrikes, battling even closer to Raqqa could prove costly for the Kurds and allied Syrian rebel factions.

Where do they come from and what do they want? The Islamic State explained.

Victory parade ... Kurdish People's Protection Units (YPG) fighters wave their movement's flag as they parade in the northeastern Syrian town of Qamishli after returning from battling Islamic State. Source: AFP Source: AFP

BATTLE OF EIN ISSA

The Britain-based Syrian Observatory for Human Rights and Kurdish activist Mustafa Bali said Kurdish fighters from the People’s Protection Units, or YPG, captured the military base on Monday night.

Later Tuesday, the Observatory and YPG spokesman Redur Khalil said Kurdish fighters and their allies took over the nearby town of Ein Issa, the last major residential area north of the city of Raqqa. The Islamic State group considers Raqqa the capital of its self-declared “caliphate” spanning Syria and Iraq.

“Ein Issa and dozens of villages around it are under our control,” Khalil said over the telephone. He said the next task is to reinforce and protect the areas ahead of any counterattack.

The Observatory said the YPG and its allies are also trying to gain control of a highway linking the northern city of Aleppo, Syria’s largest, with the northeastern city of Hassakeh.

The YPG’s official Facebook page said “dozens of Daesh mercenaries were killed” at the Brigade 93 base, using an Arabic acronym for the extremist group. The Observatory said Islamic State militants transferred the corpses of 26 of its fighters to Raqqa after they were killed in Ein Issa by airstrikes.

“Operations will continue, but it is imperative that we first attempt to secure areas under our control,” said Nawaf Khalil, head of the Germany-based Kurdish Center for Studies. “Raqqa is a vast area and attacking it will need a great deal of coordination with other groups and the international alliance.”

Aa band of about 20 IS fighters who had hidden in Ein Issa when the Kurdish troops stormed it have re-emerged, and battles are again raging in the city. Other groups of IS fighters are also engaging the Kurds on the outskirts. YPG has issued no casualty figures and there was no immediate confirmation of continuing fighting.

Front line ... A Kurdish People's Protection Units (YPG) fighter targets her rifle near near the Akcakale crossing gate between Turkey and Syria. Source: AFP Source: AFP

RAQQA PREPARES FOR SEIGE

The wives and children of IS fighters were leaving Raqqa in droves in the past few days in anticipation of a possible attack, while the militants have redeployed to positions to better defend the city, according to the Britain-based Syrian Observatory for Human Rights. The group gets its information from a network of activists across Syria.

It remained unclear whether the Kurds would push further toward Raqqa. Also, despite the recent Kurdish gains, IS militants still have another supply line from Turkey, this one running through northwestern Syria to Raqqa.

When cornered in the past, the militants have relied on coordinated mass suicide car bomb attacks and other scorched-earth tactics.

Those tactics have included mass killings. On Tuesday, a media arm of the Islamic State group in Iraq posted a video online purporting to show the killing of over a dozen men it described as spies by drowning them in a cage, decapitating them with explosives and firing a rocket-propelled grenade at them in a car.

Pushback ... An Islamc State banner lies on the ground after Kurdish forces seized an IS stronghold. Source: Supplied Source: Supplied

ISLAMIC STATE UNDER PRESSURE

The spokesman for the Islamic State group meanwhile released an audio statement promising victory despite the recent setbacks.

“God never gave the mujahedeen a promise of victory every time,” Abu Mohammed al-Adnani said in an audio message circulated by supporters yesterday. The faithful “may lose a battle or battles and may lose towns and areas but will never be defeated,” he added.

He urged Sunni Muslims to use the time of piety and dawn-to-dusk fasting as an occasion to wage jihad and seek martyrdom.

“Attack them everywhere and shake the ground beneath them,” he said in the morale-boosting message, his voice rising. “If you lose territory, you will win it back and more in the future, God willing.”

Despite the Kurds’ recent gains, the Islamic State militants still have another supply line from Turkey that runs through northwestern Syria to Raqqa.

In the audio statement, al-Adnani called on IS fighters to redouble their efforts during the Islamic holy month of Ramadan, telling supporters to “attack them everywhere and shake the ground beneath them.”

He also said IS fighters had surrounded the town of Haditha in Iraq’s western Anbar province and called on police and pro-government fighters to surrender. The IS group captured the capital of Anbar, Ramadi, last month.

“If we enter Haditha before you repent we will make you an example for generations, by God,” he said.

It was not immediately possible to verify the recording but it resembled previous audio statements from the group.

Welcome home ... Syrian Kurds celebrates as Kurdish People's Protection Units (YPG) fighters parade in the northeastern Syrian town of Qamishli after returning from battling Islamic State (IS) group jihadists in Tal Abyad. Source: AFP Source: AFP

KURDISH SPEARHEAD

The US, reluctant to put “boots on the ground” in Iraq and Syria, has found a reliable partner in the YPG, The Kurdish fighters have been the main force in the battle against the Islamic State group in Syria.

White House Press Secretary Josh Earnest called the success by the Kurds “an indication of how critically important it is for the United States to have a capable, willing and effective partner fighting ISIL on the ground.”

The Kurds are moderate, mostly secular fighters, driven by revolutionary fervor and deep conviction in their cause.

They are backed by Arab tribesmen, Assyrian Christian gunmen and members of the rebel faction known as Burkan al-Furat - Arabic for the “Volcano of the Euphrates.”

Turkey, however, considers the Kurds to be separatists and terrorists, and has placed severe restrictions on the ethnic group within its borders.

“They are a cohesive, well-trained and highly motivated force,” said Mutlu Civiroglu, a Washington-based expert on Kurdish affairs. “They are defending their homes and they know the terrain well, unlike the foreign fighters who have joined the IS.”

By contrast, Iraqi government forces and allied Shiite militiamen have been slow in retaking IS-held territory. The Iraqis have also suffered losses.