More than two years of fighting have seen the Ba'ath regime of President Bashar Al-Assad and its opponents metastasize politically and evolve militarily in ways that all but ensure a protracted and bloody stalemate in Syria. Regional and international actors' positions have also not been static, with responses ranging from efforts to find a political solution to the conflict to militarizing it, either by supporting the armed opposition or Assad. The net result is a Syria that cannot go back to the status quo ante, but cannot move forward to the point where either the regime or its opponents can decisively win and achieve tangible reductions of instability in Syria.

As the conflict drags on, Syria's civil war could further destabilize already shaky state structures in the broader Levant. It is because of the scale of what is at stake that the announcement on May 7th that US and Russian support for talks between the Assad regime and the Syrian opposition is a positive development. There should be no illusions about what international actors can and cannot do to decisively shape events in Syria. External influence matters, but what opposing local forces decide to do about a nascent political process is ultimately what matters. However, US and Russian engagement still has a role to play in shaping any effort to stabilize what is likely to be at least a decade of unrest in a Syria that will be internally divided for the foreseeable future.

A viable political process that enjoys international support may help dampen the intensity of the battle for Syria; one that both the ruling Alawites and the mainly Sunni opponents view as a battle for survival. However, Syria is also a regional arena for competition that is escalating in ways that could trigger further conflict in the Levant. Should a political process fail to take shape, it will not mean that such efforts will not be important in the future.

The regional effects of a protracted conflict may force the US to act in support of its own interests to mitigate the risks of weapons proliferation and the expansion of Jihadist groups. This may require the limited and measured use of military power in ways that do not dramatically escalate US commitments, are not driven by the unrealistic prospect of shaping a "winner" in the conflict, or raise false hopes that the US can dictate a stable conclusion to Syria's civil war on its own.

The Shifting Battlefield in Syria

In spite of the hopes and aspirations of its opponents, the Assad regime has yet to collapse under the weight of growing internal and external pressure and remains a key Iranian and Russian ally in the Middle East. While having alienated and ultimately lost much of the Ba'th party's mainly Sunni base, many Sunnis still remain on the sidelines of the country's civil war. This is in part due to the fact that the armed opposition - with more than 100 distinct rebel groups and militias - remains deeply divided and unclear about what post-Assad Syria may look like. The growing prominence of Al-Qaeda affiliated groups such as the Nusra Front has also helped regime supporters frame President Assad as the lesser of two evils.

Despite these setbacks, the armed opposition has made important gains in the north and east of Syria, and has engaged in operations at the regime's doorstep in Damascus. However,,regime supporters and the military have corporatist interests of their own and are fighting hard to defend them. Unlike Lebanon's Maronite Christians who splintered into factional and fratricidal infighting in that country's 1975 to 1990 civil war, the Assad regime has sought to channel Alawites and other minority factions into existing and new government security forces. These include the Syrian military, popular militias and the newly established National Defense Forces.

Just as opposition forces have learned key lessons in combat, so too have Assad's forces. No longer focused solely on counterinsurgency warfare, the Assad regime has maintained and expanded a significant "security zone" around Damascus. Backed up by Hezbollah and Shi'a fighters from Iraq, a major regime offensive is currently underway to retake the Qusayr pocket - a key rebel logistics hub from Lebanon, and the last major obstacle to a regime push from the south on the city of Homs. While opposition factions may be holding their own, efforts to expand these "security zones" now threaten to break opposition forces' hold on areas near Lebanon north and west of Damascus. At best, the regime hopes to break opposition supply lines and link up Latakia and Tartus in the north along the Mediterranean coast with Homs, Zabadani, the greater Damascus region and possibly down through Der'aa along the Jordanian border.

While most observers do not feel that Assad can "win," his opponents at home and abroad have underestimated his forces' fighting strength and the lengths to which Assad and its allies might be willing to go to stave off defeat. This is in part because 60-80,000 loyal troops tested in battle over more than two years of fighting are arguably more lethal than a 300,000 strong Syrian military in 2010, complacent after some 30 years of sitting idle along the Golan Heights.

One also cannot ignore the resolve of Assad's opponents either and the sheer size of the demographic pool from which it can enlist fresh fighters against the ruling regime. Like Assad, the opposition views the battle for Syria in existential "winner take all" terms. Taken together, these factors will likely lead to a protracted stalemate that neither the regime, its opponents, nor external actors like the US or Russia can decisively shape alone or in the short term.

Hezbollah, Israel and the Risks of Regional Escalation

The trajectory of Syria and efforts to deescalate the conflict have also complicated (and are complicated by) how other regional players impact war and peace in the broader Levant, especially the precarious asymmetric balance between Hezbollah and Israel.

Fearful that the loss of Assad could undermine Hezbollah both regionally against Israel and domestically as a representative of the Shi'a community, the group has been an active player in the Syria conflict in support of Assad since at least early 2012. In addition to such tasks as the defense of Shi'a villages east of the Bekaa and of the Sayyidah Zaynab Shrine - one of Shi'a Islam's holiest sites- on the outskirts of Damascus, Hezbollah veterans have been critical to helping Assad forces turn the tide in Zabadani between Damascus and the Lebanese border, and further to the north in Qusayr.

Despite its role in Syria, Hezbollah has sought to minimize its broader regional footprint, especially with regard to the UN Blue Line and potential escalation with Israel. One way this restraint could be tested is if Iran and Syria require Hezbollah to escalate along the UN Blue Line as a response to intervention in Syria. This could once again raise questions about proliferation risks should Damascus decide to try and transfer additional sensitive military hardware, such as advanced SSMs, major SAMs, ASCMs or potentially chemical weapons to the Shi'a group.

Meanwhile, Israel has had to find new ways in dealing with the kind of instability in Syria that was considered an unlikely hypothetical scenario as recently as 2010. On the one hand, the conflict meant the potential loss of a stable and predictable regional enemy in Syria along its north-eastern border and the possible emergence of Sunni political forces that are not likely to reverse decades of Syrian pro-Palestinian and anti-Israeli sentiment. On the other, the Ba'ath regime's predicament has also presented Israel with new opportunities in its efforts to curtail Iranian influence and erode Hezbollah's conventional and asymmetric capabilities.

Assad's forces are overcommitted to fight off the armed opposition, and unable to present a viable military or defensive force posture along the Israeli-occupied Golan Heights or the

UN Disengagement Observer Force (UNDOF) controlled buffer zone. Meanwhile the proliferation of opposition forces complicates Iran's efforts to safely transfer new weapons to Hezbollah. This changing environment has given Israel unprecedented margin of maneuver, especially on the strategic Golan Heights, Hezbollah's eastern flank.

There are preliminary indications that Israel now views targeting potential weapons transfers within Syrian territory with surgical strikes to be an acceptable risk that will not lead to meaningful escalation by the Assad regime or its allies. So far, Israel is alleged to have conducted at least two targeted strikes against Hezbollah-bound weapons transfers in Syria: sophisticated Buk-M2EK/SA-17 medium range SAMs in January 2013 and medium range Fateh-110 SSMs in late April.

Given the scale of regional competition and what is at stake for the so-called "Axis of Resistance," miscommunication and misperception of Israeli and US intentions in the region could lead to serious miscalculation. For example, there is preliminary evidence that Hezbollah correlated recently IDF maneuvers on the Golan and along the Blue Line with statements by the Obama Administration restating that chemical weapons would be a red line in Syria. To Hezbollah, this appeared to be the prelude to a three pronged offensive on the Shi' group: in the north-east facing Sunni rebels in Qusayr, to the south and south-east with the IDF along the Blue Line and the now unguarded Golan Heights.

This stark and complex interpretation of events by Hezbollah stands in contrast to US and Israeli goals in the Syria conflict: the US seeks to mitigate weapons proliferation, check the expanding role of transnational jihadist groups, and reach some kind of a stable political outcome in Syria. Israel, for its part, remains focused on establishing clear ground rules in the region by indicating that major weapons transfers to Hezbollah will no longer be tolerated. Neither country is seeking to escalate to the point of open confrontation or war in the Levant.

So far, neither Hezbollah, Iran nor Syria have effectively retaliated in response to Israeli efforts to curtail weapons transfers to the Shi'a group. However, it is easy to forget that just as the US and its allies make key assumptions based on intelligence and estimates, the Assad regime, Hezbollah and their allies operate in their own local and regional contexts and are at least as susceptible as their opponents to "group think," over-estimation, and misinterpretation. Chemical weapons - and what to do about them if they were used by either the regime or the opposition - and weapons transfers to non-state armed groups only serve to further complicate this picture.

The Uncertain Trajectory of Syria and the Region

There is no guarantee that any of these patterns will become predictable or stable as the conflict drags on. Assad and his opponents are not likely to reach a point where one can eliminate the other on the battlefield. Assad is pushing for an Alawite enclave to the west, at a minimum along the Mediterranean coast, in Homs and south through Damascus. In turn, opposition factions control Sunnis strongholds to the north and east with Homs and the Orontes River becoming key dividing lines.

While talk of partition may be premature, a form of "soft" partition - wherein the boundaries of the country remain, but the internal political and sectarian boundaries change - is now all but reality. The "zero sum" approach of the regime and the opposition on what a political process could and should look like is untenable. Assad will not relinquish leadership of the regime and the Alawites unless an externally backed political process takes shape that ensures their long-term autonomy.

The opposition in turn needs strong leadership if it is to have a chance of playing a role in governing a divided and unstable Syria, let alone find the means of controlling if not eliminating Al-Qaeda affiliates in Syria. There is little chance that groups opposed to Hezbollah but also opposed by the US and more moderate form of governance in Syria - especially the Al-Qaeda in Iraq affiliated Nusra Front - will simply fade into the night.

The regional instability dimension of the Syria conflict further complicates this situation. While Iran and Hezbollah may be too committed at home or in the region to retaliate, the same may not be true of Assad should the regime truly feel threatened with intervention or a major reversal. It is no stretch to assume that it fears the former far more than the latter. In his quest for Alawite autonomy, the stakes are so high that Assad may escalate in ways that may appear erratic. This may include continued efforts to transfer weapons to Hezbollah despite the certainty that Israel will retaliate, targeting US and allied assets with ballistic missiles, resorting to chemical weapons scare tactics, and asymmetric attacks against US or allied interests in the Levant.

Diplomacy and its Alternatives in Syria

While these forces drive local dynamics in Syria, an international process backed by the US and Russia will be critical to shaping the politics of the "new" Syria. In addition, important as US and Russian led talks may be in shaping the trajectory of Syria's internal conflict, they could play an equally important role in efforts to deescalate broader regional tensions, especially between Israel and Hezbollah in the Levant, and indirectly vis-à-vis Saudi-Iranian and Sunni-Shi'a competition in the broader Middle East. While many expect diplomacy to fail, Lebanon's fifteen year sectarian civil war showed that efforts to end the conflict come and go until one lines up with local, regional and international dynamics shaping the conflict.

Absent a political process, there are no good military options if the objective is to end the conflict and stabilize Syria. Taking out key chemical weapons infrastructure - unilaterally or otherwise - sends a clear signal to Assad and his opponents. However, so-called "red lines" on chemical weapons are largely artificial as such systems are neither the ones doing the most damage, nor are they the most important strategic threat to the region. Targeting these holding also does nothing to end the civil war. Arming the rebels or creating buffer zones along the Turkish and Jordanian borders gives regime opponents some breathing room, but it does little to address threats posed by chemical weapons and their proliferation. Injecting limited or massed US forces into an active civil war may also lead to unintended consequences, including the death or capture of US forces by Assad forces and their allies, including Hezbollah in neighboring Lebanon.

Given these limitations, and should diplomacy fail to make tangible gains, the US may have to accept that it cannot decisively shape who "wins" in Syria's civil war, or that it can decide the outcome of the conflict alone. However, none of the key risks that concern US policy makers - including the proliferation of chemical weapons, modern anti-air and anti-armor weapons systems, or the emergence of Al-Qaeda affiliated groups - are going to dissipate or diminish on their own.

Accordingly, this could lead to the limited use of US military power in Syria. Military power would not be used to support one faction in Syria's civil war over another. It also would not be used in ways that could rapidly escalate into mission creep and trying to achieve the impossible in Syria. It would not also be used to decide the outcome of the conflict, or to shape a political process. How US military power could be used is to selectively target risks tied to proliferation of chemical weapons and other strategic capabilities in Syria. It could be used to contain and curtail the expansion of Al-Qaeda in the Levant, and to prevent the preeminence of radical forces in the region.

Such scenarios will not endear the US to Syrians or the broader Arab world, and while it is understandable that Washington should want to maintain positive public attitudes in the region, hard choices in foreign policy making are not driven by popularity contests. The Syrian conflict may permanently alter the post-Sykes-Picot and post-WWII Middle East state structure and regional security architecture. What that does not alter, however, is US preferences for managing instability in the region.