The terror movement has also failed to conquer the symbolic town of Kobani (Ayn al-Arab) close to the Syrian-Turkish border (further south, Islamic State losses have been more modest and at least partially reversed).
Yet despite these setbacks, there are no indications that Islamic State is anywhere close to collapse. And while American bombers and Kurdish fighters are preventing its advance further east, there are many indications the jihadists are continuing to advance their presence in a south and westerly direction – from the borders of their entity towards Damascus and Lebanon, and incidentally, in the direction of Israel.
A largely hidden contest is under way in Deraa province in southern Syria, between Islamic State and the rival jihadists of Jabhat al-Nusra.
Deraa, where the Syrian rebellion was born in March 2011, has been the site of major losses for the Assad regime over the last year. Nusra established itself as a major force in the area after its fighters were defeated by Islamic State further east.
In recent weeks, reports have emerged that three rebel militias in Deraa have pledged bay'ah (allegiance) to Islamic State.
In recent weeks, reports have emerged that three rebel militias in Deraa have pledged bay'ah (allegiance) to Islamic State. The largest of these is the Yarmuk Martyrs Brigade; the others are Saraya al-Jihad and Tawheed al-Junub. While the Yarmuk Martyrs Brigade has since denied pledging formal allegiance to Islamic State, the reports have Nusra and the Western- supported rebel groups in the south nervous.
They are acutely aware that in locales further east, such as al-Bukamal on the Syria-Iraq border, in the course of 2014 Islamic State came in not through conquest, but by recruiting the non-Islamic State groups that held the area to its flag. Nusra now fears that Islamic State wishes to repeat this process further south.
This fear is compounded by the appearance of Islamic State-linked fighters in the Damascus area in recent weeks. In the town of Bir al-Qasab, fighters affiliated with the terror movement have been battling other rebels since early December; Islamic State has engaged in resupplying these fighters from its own territory further east. Nusra and other rebel groups have begun to speculate about the possibility of a push by the jihadists either toward Deraa or Eastern Goutha, adjoining Damascus.
Finally, further west, in the Qalamoun Mountains, Islamic State and Nusra fighters have clashed in recent weeks. Reports have surfaced that Islamic State has begun to demand that other rebel groups in the area, including Nusra, pledge bay'ah to it.
This is despite the notable fact that the Qalamoun area had been the scene in recent months of rare cooperation between Islamic State and Nusra, out of shared interest in extending the conflict into Lebanon.
The events there come amid Lebanese media speculation as to the possibility of an imminent Islamic State push from Qalamoun toward the Sunni town of Arsal across the border (or even, in some versions, toward the Shi'ite towns of Baalbek and Hermel).
Such an offensive would form part of the larger campaign against the regime and Hezbollah in this area.
SO, WHAT does this all amount to? First, it should be noted that Nusra's presence in Quneitra Province, immediately adjoining the Golan Heights, is the point at which Syrian jihadists currently come closest to Israel.
As Islamic State loses ground further east, it seeks to recoup its losses elsewhere; this trend is bringing jihadists closer, toward the borders of both Israel and Jordan.
But Nusra, unlike Islamic State, appears genuinely committed to the fight against Syria's Assad regime. And at times, at least, it is prepared to set aside its own ambitions to pursue this general goal.
This means, from Israel's point of view, that while its presence close to the border is a matter of long-term concern, in the immediate future the al-Qaida franchise's attentions are largely turned elsewhere.
Such calculations could not be safely made regarding Islamic State, which by contrast works only for its own benefit.
Its sudden push into Iraq in June and then August show the extent to which it is able to abruptly change direction, catching its opponents by surprise. The record of Islamic State against other rebel groups thus far has been one of near uninterrupted success.
Conversely, it is now being halted in its eastern advances by the US and its allies. But neither the US Air Force nor the Kurdish ground fighters are present further south and west, so there is a clear strategic logic to the current direction of Islamic State activity.
As Islamic State loses ground further east, it seeks to recoup its losses elsewhere; this trend is bringing jihadists closer, toward the borders of both Israel and Jordan. It may be presumed this fact is not lost on Israeli defense planners – hence the reports of increased activity by Military Intelligence collection units and reinforcement of the military presence on the Golan Heights.
The single war now raging in Syria, Iraq and increasingly Lebanon, is moving closer – toward Israel.
Jonathan Spyer is director of the Global Research in International Affairs (GLORIA) Center and a fellow at the Middle East Forum.