These reports are sure to increase anxiety among Israel and other opponents of the Iranian regime’s apparently expanding military influence in the Middle East. The S-300 missile defense system improves Iran’s defensive capabilities against possible airstrikes on its nuclear or military infrastructure, but it also may preface a general expansion in Iran’s military arsenal, as well as the use of that arsenal in foreign conflicts.

On Tuesday, Vice Admiral John Miller and American Enterprise Institute scholar Frederick Kagan published an editorial at Fox News which described the S-300 transfer as the first instance of Iran “muscling up” in a way that will ultimately demand a response from Western powers. The article observed that the finalization of the S-300 deal coincided with the development of a six billion dollar “shopping list” of other advanced military equipment that Iran wishes to procure from its Russian partners.

That equipment includes an anti-ship missile, long-range jet fighters and bombers, and a battle tank. At the same time that Iran is engaged in talks to obtain these weapons, it also claims to be expanding domestic production of weapons that include a battle tank that is comparable to the desired Russian T-90.

The US technically has the ability to block weapons sales to Iran in the UN Security Council if Russia decides to go ahead with them. But the Fox News article also observes that Iran has struck a defiant tone regarding these restrictions, and apparently with good cause. The rules that allow for such obstruction by the Security Council do not specify consequences for ignoring the restriction. Thus it is possible that Russia will see those consequences as being insufficient to outweigh the benefit of further expanding its relations with Iran.

The extent of that benefit may depend upon to the extent to which Iranian and Russian interests in the Middle East converge or diverge at the present time. And a Reuters reports about the Syrian Civil War, where both Iran and Russia have been backing the Assad regime, suggests that the alignment of their interests is very unclear.

That is, in recent days there have been inconsistent claims about the intentions of the Syrian regime and its backers in the midst of an internationally brokered ceasefire among most of the combatants in the multi-party war. On one hand, the Russian Defense Ministry denied that it had been planning an assault on the Syrian city of Aleppo over the weekend. But on the other hand, the Syrian government claimed that its forces had been planning such an attack on the understanding that they would be supported by Russia warplanes.

Backing up the latter claims, Syrian rebel groups claimed that both Syrian and Russian forces had resumed and intensified bombing in the area, in apparent violation of the ceasefire. Last week, the National Council of Resistance of Iran similarly observed that Iranian Revolutionary Guard Corps forces and their Shiite militant proxies had been massing for a major offense at Aleppo.

By contrast, the Russians claimed that it was the militant, anti-Assad Al Nusra Front that was massing at that location. The Al Nusra Front, along with the Islamic State of Iraq and the Levant, is not covered by the ceasefire, as foreign parties attempt to focus the attention of the Assad regime and the moderate rebel groups against the Al Qaeda affiliated terrorist organizations.

The complicated division of warring factions at Aleppo helps to make that city a major stumbling block in the supposed cessation of hostilities, according to Reuters. Clearly, the moderate rebels and the pro-Assad forces are each trying to blame the other side for the continuation of conflict in that region. What’s more, the Syrian Foreign Ministry has also attempted to assign blame to Turkey and Saudi Arabia, which back some of the same rebel groups as the US does.

While it may be difficult to say with certainty who is the primary aggressor at Aleppo, one thing that we do know is that at least four Iranian soldiers have been killed in fighting there, according to Arutz Sheva. These deaths indicate a continued Iranian presence on the frontlines, and the regime’s response to those deaths seems aimed at justifying even greater engagement.

Arutz Sheva also points out that 220 Iranian fighters have been killed in Syria in the past six months, seemingly undermining the claim that Iranian forces are merely advisors to the Assad regime’s military.

If Iran continues to expand its own presence in the conflict, Russia may or may not follow suit. The convergence or divergence of these two forces in Syria may go a long way toward indicating the strength of their alliance and thus the likelihood of Russia providing Iran with more advanced weapons to commit to the same war.