A survey of Russian anti-aircraft batteries, using commercial satellite photos, has shown that Russia has been shutting down S300 (surface to air missiles) batteries around Russian cities and moving the missiles and launchers to the Ukrainian border, where the missiles are used to attack surface targets. The new S400 SAM began replacing S300s about fifteen years ago, but progress has been slow because of economic sanctions imposed in 2014 and 2022, The military budget has declined and the S300 missiles, radars and launchers are not getting any upgrades because the S400 is much more effective (with twice the range of the S300) and one S400 battery can do the work of two or more S300 batteries. Mainly this is about the sanctions making it impossible for Russia to manufacture new guided missiles to use against Ukraine. This is why there have been fewer guided missiles used against Ukrainian targets in the last month but a lot more less accurate unguided missiles and S300 SAMs. At least 500 S300 missiles have been used so far against surface targets in Ukraine and there are still 7,000 S300 missiles available for hitting surface targets. Some S300 batteries are still used in Ukraine or from Russia. Not a lot of these are needed because the Ukrainians have developed systems and tactics that minimize the effectiveness of the S300 as a SAM.
Back in July Ukraine warned that Russia was beginning to use its 1.8-ton S300 (SA-10) SAMs as SSMs (surface to surface missiles). The allegation was based on Belarus revealing that they had recently tested S300s used as SSMs. The S300 was known to have been designed with SSM capability. That means one of launch options includes SSM mode. There are two major limitations to using a SAM as an SSM. One is accuracy at longer ranges. Russian SAMs are guided to the target using a ground-based targeting radar that guides the S300 to aerial targets up to 150 kilometers away. SAMs are programmed to self-destruct if they miss their target so that the missile and its small (100-200 kg) warhead does not land on friendly territory. Used as an SSM the self-destruct is disabled and the guidance system aims the missile at a ground location, but with less accuracy than against aerial targets. Russia has apparently modified the SSM option to include a GPS option that directs the SAM to a specific ground location. The GPS option works, but not as accurately as expected. Ukraine believes that the Russians are running out of SSM missiles and using S300s as SSMs because there is not much need for their SAM capabilities, especially with the more recent and capable S400 now available. The Ukrainian prediction was apparently correct.
The Ukrainian prediction was based on recent events involving SAMs as SSMs. Israel had some recent experience with this when a Syrian S200 missile was deliberately used against a military facility deep inside Israel. This took place in early 2021 when a missile from Syria landed a few kilometers from the Israeli Dimona nuclear research center. There was no damage because Dimona is 300 kilometers south of the Syrian border in a rural desert area. First thoughts were that this was another Iranian attempt to carry out some credible revenge for the recent Mossad operation that destroyed the underground Natanz nuclear fuel enrichment facility. If this was a deliberate missile attack, it failed, but it meant Israel spending a lot of money firing expensive ABM (anti-ballistic-missile) missiles at more Syrian anti-aircraft missiles that cross the border either accidentally or on purpose. Israel is trying to solve this problem by modifying its ABM fire control software to discriminate between the trajectories of SAMs that are not headed for civilian or military targets and those that are. The Israeli Iron Dome system has long used such a method to only shoot down targets headed for targets that must be defended.
Initial examination of the impact area debris near Dimona revealed it was a S200 (SA-5) SAM, a SAM that had been accidently landing for years after missing intended aircraft targets. For example, in 2017 Israel used an Arrow 3 anti-missile missile to intercept a Syrian S200 that had been fired at Israeli jets bombing a target in eastern Syria near Palmyra. Apparently several S200s missed the Israeli jets and instead of detonating anyway, as these missiles are programmed to do, continued into Israeli air space and an Arrow 3 ABM missile was fired just in case the incoming threat was a ballistic missile. At the time it was suspected that Syria might have deliberately modified some of their seven-ton S200 missiles to operate as surface-to-surface missiles. This has been done before with Russian SAMs, usually as an unofficial (and crude) modification by Arab users.
There have been several existing SAMs with a built-in surface-to-surface mode. This was done for the U.S. Nike-Hercules SAMs that entered service in the 1960s and some are still around. Other users of the Nike-Hercules (like Taiwan and South Korea) improved this SSM option and produced an accurate, if expensive, surface-to-surface short range ballistic missile. The Nike-Hercules was designed for potential use as a surface-to-surface weapon. The U.S. Navy has added a SSM capability to their SM 6 SAM and recently tested it successfully against stationary targets. This mod is meant to give SM-6 an anti-ship missile capability. Earlier U.S. Navy SAMs also had this SSM capability.