Russian President Vladimir Putin announced Monday he was lifting a ban on the sales of the S-300 missile defense system to Iran. The system is intended to protect against missiles, rockets and hostile aircrafts, and has different versions with different varying capabilities.
The initial sale was completed in 2007-2010, but never actualized because of Israeli and US pressure. But Monday's news might not be as dangerous or earth shattering as the Russians and Iranians would want you to think.
During the time of the initial sale, Israel was reluctant to sell UAVs and advanced weapons systems to Georgia, Russia's local foe. At the same time, the Russians were training Iranians – including elite Revolutionary Guard forces – in the system's workings on Russian soil.
Should the Iranians receive the system any time soon, it would be operational very quickly. Moreover, it would not be farfetched to assume that some parts of the S-300 system (like radar or some of its controls) have already arrived in Iran, even if the launchers have yet to do so.
It is hard to assess to what extent an Iranian-controlled S-300 will hinder the ability of Israel, the US or Arab states to attack Iranian nuclear and military facilities. Firstly, we don't know exactly what make of the S-300 Russia plans to transfer to Iran or its effective range for ballistic missiles, rockets or cruise missiles fired from over 150 km.
Secondly, both the Israeli and the American air forces, as well as the American fleet, have trained in Cyprus, Greece and other places where Russian technology is available, and thus it is safe to assume they are well-versed in the system's ins-and-outs. It is also safe to assume they have developed technological means to evade the system's defense mechanisms.
Generally, the S-300 is in use in many countries and is even manufactured in China. The lengthy time between sale and delivery of the system to Iran gave the West ample time to prepare for its deployment in the Iranian context.
Therefore we can assume that its delivery to Iran will not dramatically hinder Israel's – or any other state's – ability to launch a military strike against Iran's nuclear facilities, if only because contemporary deployment tactics were developed having taken the system into account.