ISIS reinforces its Syrian stronghold of Raqqa as Kurds get closer

By Salma Abdelaziz, CNN
3 minute read
Updated 3:59 AM EDT, Thu June 25, 2015
Wounded passengers are treated following a suicide bombing at the Brussels Airport on March 22, 2016. <a href="http://www.cnn.com/2016/03/30/europe/brussels-investigation/index.html">The attacks on the airport and a subway </a>killed 32 people and wounded more than 300. ISIS claims its "fighters" launched the attacks in the Belgian capital.
Wounded passengers are treated following a suicide bombing at the Brussels Airport on March 22, 2016. The attacks on the airport and a subway killed 32 people and wounded more than 300. ISIS claims its "fighters" launched the attacks in the Belgian capital.
Ketevan Kardava/Getty Images
Syrians gather at the site of a double car bomb attack in the Al-Zahraa neighborhood of the Homs, Syria, on February 21, 2016. <a href="http://www.cnn.com/2016/02/21/middleeast/syria-civil-war/index.html" target="_blank">Multiple attacks in Homs and southern Damascus</a> kill at least 122 and injure scores, according to the state-run SANA news agency. ISIS claimed responsibility.
Syrians gather at the site of a double car bomb attack in the Al-Zahraa neighborhood of the Homs, Syria, on February 21, 2016. Multiple attacks in Homs and southern Damascus kill at least 122 and injure scores, according to the state-run SANA news agency. ISIS claimed responsibility.
STRINGER/AFP/Getty Images
Syrian pro-government forces gather at the site of a deadly triple bombing Sunday, January 31, in the <a href="http://www.cnn.com/2016/01/31/middleeast/syria-damascus-explosions/index.html" target="_blank">Damascus suburb of Sayeda Zeynab</a>. ISIS claimed responsibility for the attack, according to a statement circulating online from supporters of the terrorist group.
Syrian pro-government forces gather at the site of a deadly triple bombing Sunday, January 31, in the Damascus suburb of Sayeda Zeynab. ISIS claimed responsibility for the attack, according to a statement circulating online from supporters of the terrorist group.
LOUAI BESHARA/AFP/Getty Images
Yemenis check the scene of a car bomb attack Sunday, December 6, in Aden, Yemen. <a href="http://www.cnn.com/2015/12/06/middleeast/yemen-aden-governor-killed/index.html">Aden Gov. Jaafar Saad and six bodyguards died in the attack</a>, for which the terror group ISIS claimed responsibility.
Yemenis check the scene of a car bomb attack Sunday, December 6, in Aden, Yemen. Aden Gov. Jaafar Saad and six bodyguards died in the attack, for which the terror group ISIS claimed responsibility.
Wael Qubady/AP
Investigators check the scene of a mosque attack Friday, November 27, in northern Bangladesh's Bogra district. <a href="http://www.cnn.com/2015/11/27/asia/bangladesh-isis-attack-claim/index.html" target="_blank">ISIS has claimed responsibility for the attack</a> that left at least one person dead and three more wounded.
Investigators check the scene of a mosque attack Friday, November 27, in northern Bangladesh's Bogra district. ISIS has claimed responsibility for the attack that left at least one person dead and three more wounded.
AP
Wounded people are helped outside the Bataclan concert hall in Paris following a series of coordinated attacks in the city on Friday, November 13. The militant group ISIS claimed responsibility <a href="http://www.cnn.com/2015/11/13/world/gallery/paris-attacks/index.html" target="_blank">for the attacks,</a> which killed at least 130 people and wounded hundreds more.
Wounded people are helped outside the Bataclan concert hall in Paris following a series of coordinated attacks in the city on Friday, November 13. The militant group ISIS claimed responsibility for the attacks, which killed at least 130 people and wounded hundreds more.
YOAN VALAT/EPA/LANDOV
Emergency personnel and civilians gather at the site of a <a href="http://www.cnn.com/2015/11/16/middleeast/beirut-explosions/" target="_blank">twin suicide bombing</a> in Beirut, Lebanon, on Thursday, November 12. The bombings killed at least 43 people and wounded more than 200 more. ISIS appeared to claim responsibility in a statement posted on social media.
Emergency personnel and civilians gather at the site of a twin suicide bombing in Beirut, Lebanon, on Thursday, November 12. The bombings killed at least 43 people and wounded more than 200 more. ISIS appeared to claim responsibility in a statement posted on social media.
Bilal Hussein/AP
Smoke rises over the northern Iraqi town of Sinjar on November 12. Kurdish Iraqi fighters, backed by a U.S.-led air campaign, <a href="http://www.cnn.com/2015/11/13/middleeast/iraq-free-sinjar-isis/" target="_blank">retook the strategic town, </a>which ISIS militants overran last year. ISIS wants to create an Islamic state across Sunni areas of Iraq and Syria.
Smoke rises over the northern Iraqi town of Sinjar on November 12. Kurdish Iraqi fighters, backed by a U.S.-led air campaign, retook the strategic town, which ISIS militants overran last year. ISIS wants to create an Islamic state across Sunni areas of Iraq and Syria.
Bram Janssen/AP
Syrian government troops walk inside the Kweiras air base on Wednesday, November 11, after they broke a siege imposed by ISIS militants.
Syrian government troops walk inside the Kweiras air base on Wednesday, November 11, after they broke a siege imposed by ISIS militants.
SANA/AP