In early 2021 Russia was observed improving its Syrian Hmeimim airbase and nearby naval base in the port city of Tartus. Russia has had access to Tartus since 1971, when the Soviet Union signed a deal with Bashar al Assad, the father of the current Assad running Syria, for its warships to use the port of Tartus. Russia never established a naval base at Tartus but because of the 1971 agreement, usually had a few dozen officers, sailors and civilian specialists working in Tartus to arrange resupply for visiting Russian warships, which sometimes headed for Tartus to make some minor repairs that needed parts or tech assistance that could only be obtained in a friendly port. This arrangement continued until 2013, when the Syrian civil war began and Russia pulled its personnel out of Tartus. Russia returned in 2015, with a major military intervention that played a major role in defeating the rebels. Most of the Russian support was logistical. That means military supplies and help repairing or refurbishing Russia tanks, artillery and other systems bought from Russia. The other major item was air support for Assad forces. Since 2013 over 45,000 sorties have been flown from Hmeimim, most of them combat airstrikes or reconnaissance and surveillance to find targets. Another 5,000 combat sorties were flown from Russia. The Russian airstrikes did major damage to Assad opponents, which often included pro-rebel civilians that Syrian and Russian warplanes attacked in an effort to get the civilians to leave their homes and even Syria. That was considered to be a war crime but no one has yet made a move to prosecute Russia or Syria for this and, as long as the Assads can stay in control of Syria, they will never be prosecuted for that or similar attacks made before 2013 to suppress local opposition.
To carry out that kind of air support Russia needed an airbase. By 2015 all the major Syrian military air bases were either in enemy hands or cut off from the coast, where most of the supplies for an air campaign were to be delivered by ship. The solution was a new military airbase, built by Russia next to the main airport outside Latakia City, the capital of Latakia province. Latakia City was also a port and could handle the cargo ships bringing in supplies for the new Russian base. The new Hmeimim airbase was built next to the airport, which was initially used for some of the Russian military sorties until the new Hmeimim facilities became operational. That happened by the end of 2015 and by the end of 2016 the Russian Air Force no longer has to use airport facilities any longer. Hmeimim airbase is 85 kilometers north of the port of Tartus and 50 kilometers from the Turkish border. Both are in Latakia province, which also contains the Syrian Mediterranean coastline and a very pro-Assad population.
In 2018 Syria and Russia signed a new treaty expanding and legalizing Russia control over their growing Tartus base and the Hmeimim air base. Thus included a 49-year lease deal. In 2020 Syria agreed to expand the 2018 agreement and provide Russia with additional land next to Hmeimim for an expansion. The latest round of Hmeimim improvements include extending an airstrip several hundred meters.
Initially Hmeimim had air-conditioned accommodations for about a thousand Russian personnel. That was more than doubled by 2018 as the air and ground defenses of Hmeimim were upgraded. While some Assad loyalists were employed for external security, Russians handled that inside the base, which did not include air defense systems and additional surveillance radars and electronic weapons.
The latest improvements in Tartus are even more extensive as they include construction of a floating dock for repairing warships or commercial ships that would otherwise have to use Russian ports in the Black or Baltic Seas. The floating drydock can be built more quickly than a conventional (in the ground) drydock. The floating drydock can be moved (via a tow) and can last a long time if kept in a sheltered port.
Tartus now has storage facilities for fuel, ship repair materials and tools as well naval munitions. Tartus is turning into the largest for foreign naval base Russia has ever had.