A a collection of some of Syria’s  most powerful rebel groups have publicly abandoned the opposition’s political leaders, casting their lot with an affiliate of Al Qaeda.  As support for the Western-backed leadership has dwindled, a second, more extreme Al Qaeda group has carved out footholds across parts of Syria, frequently clashing with mainline rebels who accuse it of making the establishment of an Islamic state a priority over the fight to topple President Bashar al-Assad….The deep differences between many of those fighting in Syria and the political leaders who have represented the opposition abroad spilled into the open late Tuesday, when 11 rebel groups issued a statement declaring that the opposition could be represented only by people who have “lived their troubles and shared in what they have sacrificed.”

Distancing themselves from the exile opposition’s call for a democratic, civil government to replace Mr. Assad, they called on all military and civilian groups in Syria to “unify in a clear Islamic frame.” Those that signed the statement included three groups aligned with the Western-backed opposition’s Supreme Military Council….The rebel groups that assailed the political opposition are themselves diverse and include a number that are linked to the coalition’s Supreme Military Council. More troubling to the West, they also include the Nusra Front, a group linked to Al Qaeda. At the same time they include groups that remain opposed to another group linked to Al Qaeda: the Islamic State in Iraq and Syria…

Further complicating the picture is the rise of the new Qaeda franchise, the Islamic State in Iraq and Syria, which has established footholds across northern and eastern Syria with the intention to lay the foundations of an Islamic state.  In recent months, it has supplanted the Nusra Front as the primary destination for foreign jihadists streaming into Syria, according to rebels and activists who have had contact with the group.  Its fighters, who hail from across the Arab world, Chechnya, Europe and elsewhere, have a reputation for being well armed and strong in battle. Its suicide bombers are often sent to strike the first blow against government bases.

But its application of strict Islamic law has isolated rebels and civilians. Its members have executed and beheaded captives in town squares and imposed strict codes, forcing residents to wear modest dress and banning smoking in entire villages.

Excerpts, BEN HUBBARD and MICHAEL R. GORDON, Key Syrian Rebel Groups Abandon Exile Leaders, New York Times, Sept. 25, 2013