Syrian rebels fighting with al-Nusra Front, al Qaeda's offshoot in Syria, seized the Brigade 82 army base in the southern province of Dera'a Sunday, rebels fighting in the area told the International Business Times in a Skype interview. The base sits in a strategic position in Dera'a, allowing those controlling it to fight with relative ease and protection, and providing access to fire on rebels in nearby villages.

The base is situated along the border with Jordan and lies just outside the military zone protecting Damascus. It is the closest rebel-held base to the capital.

The seizure is a major win for the rebels in the South. It will allow them to take control of major supply and transportation routes that lead to cities such as Homs and Idlib. It also gives the rebels better access to the Jordanian border where hundreds of thousands of refugees have fled in the last four years. 

For at least a year, Syrian rebels have failed to advance in the southern part of the country. The main fighting has taken place around Aleppo, near the Turkish border, and intensified with the infiltration of militants from the Islamic State group, also known as ISIS or ISIL. In the past six months in particular, the intense fighting in the North and the constantly shifting alliances between groups has limited the success of rebels funded and backed by the U.S.

Secretary of State John Kerry said in December the U.S. was engaging in new efforts to save moderate Syrian rebels in the northern part of the country from total defeat. Those rebels, he said, "did not fare well in their battles and one or two of them folded into al-Nusra, which is disturbing." The rebels are, according to Republican Sen. John McCain, "on the verge of collapse."

IBTimes also reported the U.S. had withdrawn weapons support for the moderate rebel groups and was searching for new fighters to prop up. Following that statement, Islamist factions captured several army bases in Idlib province, giving groups like al-Nusra access to a highway that leads directly to Damascus. 

Al-Nusra rebels who took the base in Dara'a Sunday are fighting alongside groups connected to the western-backed rebels in the North. It is still unclear, however, which groups, if any, are still receving U.S. aid.