Putin’s invasion of Ukraine has reminded the international community that war in the 21st century is indeed a real possibility, despite the insistence by many that Russia would not invade Ukraine throughout the months-long build-up of its forces along the Ukrainian border.

The pre-war positioning of ground forces along the frontier from 2021 to 2022, however, was not the beginning of the Kremlin’s preparations for war with Ukraine, nor has the ground war been the only dimension of the conflict. Rather, the February invasion was the culmination of decades of Russian aggression in the Black Sea to reshape the regional status quo and achieve dominance as the leading Black Sea naval power.

Since the collapse of the Soviet Union in 1991, Russia and Ukraine have been at odds over Black Sea security issues. The earliest dispute was rooted in the dissolution of the Soviet Union itself. The Soviet Black Sea Fleet and its assets were based in the Ukrainian administered port of Sevastopol on the Crimean Peninsula. Following drawn-out diplomatic talks, a series of agreements concluded in the late 1990s allowed for the division of fleet assets between the two states, the lion’s share going to Russia in exchange for financial compensation, and allowing it to lease naval facilities in Crimea to house its vessels and personnel. These agreements and a 2010 renewal treaty were abrogated by Russia following its unilateral annexation of Crimea in 2014.

The first significant flashpoint in the long-running Russo-Ukrainian maritime rivalry, however, was the 2003 Tuzla Island dispute. The Kremlin, seeking to circumvent Ukrainian tolls and likely undermine the possibility of future NATO basing in the Sea of Azov, began the unannounced construction of a dam in part of the Kerch Strait which straddles the Russo-Ukrainian maritime borders in the Sea of Azov and the Black Sea. As tensions grew, diplomacy once again produced a new bilateral treaty, the 2003 Treaty on the Legal Status of the Sea of Azov and the Kerch Strait, declaring the Sea of Azov as a joint internal waterway of Ukraine and Russia. It was a good deal for Vladimir Putin early in his presidency: skirting Ukrainian tolls, complicating non-commercial third-party navigation into the Sea, and securing its ability to sail warships into and out of the Sea at will.

Five years later, the Kremlin secured another win. When the 2008 Russo-Georgian War broke out, Russian forces were able to intervene and secure their strategic objectives in just five days. This effectively ratified the breakaway regions of Abkhazia and South Ossetia’s de facto independence from Georgia. There are two key geopolitical implications resulting from this short war: that roughly two-thirds of Georgia’s Black Sea coastline was cut-off and now under the control of a pro-Russian separatist state relying on Russian patronage; and that while Georgia was promised NATO membership, that bid would be indefinitely delayed. Thus, Russia effectively pacified the eastern side of the Black Sea by late 2008. Moreover, the conflict marked the beginning of the end for the Black Sea Naval Cooperation Task Group, a forum for the sea’s naval powers to work together — Georgia and Russia both refused to participate in naval drills involving the other. Equally important, the mixed operational performance of Russian forces during the war in Georgia ushered in a near-decade of military reform, seeking to improve Russian doctrine and capabilities for its future efforts to reshape the Black Sea region.

Russia’s actions against Georgia did finally sound an alarm in the West, but ultimately the international response was muddled and intangible. Diplomatic overtures culminated in the 2009 meeting of then-US Secretary of State Hillary Clinton and Russian Foreign Minister Sergey Lavrov. The “Russia Reset” seemed to usher in a new Washington-Moscow détente, as the Obama administration canceled the Bush plan for a missile defense system in Poland and the Czech Republic in 2009, concluded the New START Treaty to reduce nuclear arms in 2010, agreed to new sanctions on Iran with Russia and China in the same year, and lifted some sanctions on Russian state companies. Already though, friction between the US and Russia on the Syrian Civil War, the Magnitsky Act, and other issues were feeding doubts about Putin’s intentions.

Russia’s Black Sea Fleet played a part in this. In 2015, Russia greatly escalated its involvement in the Syrian Civil War, utilizing elements of the fleet to support the Mediterranean Squadron, a sub-formation, with efforts including naval fire and troop transport.

But it was in 2014 that any remaining questions about Kremlin goodwill vanished. The Kremlin ordered so-called little green men (unbadged Russian troops) into the Crimean Peninsula, leading to its annexation the same year. Shortly after, Russia launched its first invasion of Ukraine, sending troops and equipment to back separatist movements in the easternmost provinces of Donetsk and Luhansk. Fighting in the area has continued ever since, leaving at least 14,000 dead.

A less well-appreciated aspect of the Russian campaign at the time was the crippling of Ukraine’s maritime capabilities. Ukraine lost a third of its Black Sea coastline, it’s landward half of the Kerch Strait which dominates access to the Sea of Azov, and several key port cities, none more significant than Sevastopol. The city had been the chief base of the Ukrainian Navy since gaining independence from the Soviet Union in 1991. It had also been home to the Soviet Union’s naval academy which has since been repurposed for Russian usage. During the annexation, much of the Ukrainian fleet was in port across Crimea and roughly 80% of its fleet was captured by Russian forces. Additionally, three major shipyards were lost, and have since been repurposed to build Russian vessels.

Thus, by the beginning of 2015, Russia had nearly doubled its own Black Sea coastline at the expense of Ukraine, relegated the Ukrainian Navy to a paltry force, significantly undercut Ukraine’s domestic naval infrastructure, marginalized another neighbor on the Black Sea by propping up an autonomous state occupying two-thirds of its coastline, and secured command of access to the Sea of Azov.

Russia’s geographical dominance of the northern Black Sea by 2015 elevated the status of the Black Sea Fleet. Over the next several years, it would undergo major modernization efforts, largely made possible by the seizure of Crimea. Of course, several looming issues affected the course of the naval buildup, from the Montreux Convention’s various limitations on warships in the region, to more basic budgetary concerns. Addressing both factors, fleet modernization focused on submarines and smaller Kalibr missile-armed vessels. Additionally, the shift from leased bases in Crimea to complete occupation of the landmass allowed Russia to deploy land-based anti-ship and anti-aircraft systems to the peninsula, thereby extending its anti-access area denial capability.

Within the Black Sea region, Russia has repeatedly rubbed up against Ukraine with the seizure of its vessels and the occasional closing of the Kerch Strait. The latter has been facilitated by Russia’s completion of the Kerch Bridge, which has not only connected Crimean territory seized in 2014 to mainland Russia, but also further narrowed the straits for easier barricading. Indeed, in the lead up to its invasion, Russia again closed large swaths of the northern Black Sea and Sea of Azov.

Meanwhile, NATO visitors, never welcome, are now greeted with open hostility. Last year, Russian air and naval assets were dangerously shadowed, and reportedly fired near the British destroyer HMS Defender as it conducted a freedom of navigation patrol, later repeating its dangerous actions close to the Dutch frigate HNLMS Evertsen, which had previously patrolled with Defender.

This is part one of a two-part series on Black Sea security.

Retired Navy Admiral James G. Foggo III is a distinguished fellow at the Center for European Policy Analysis and former commander of U.S. Naval Forces Europe and Africa, and Allied Joint Force Command, Naples. He commanded BALTOPS in 2015 and 2016 and Exercise Trident Juncture in 2018.

Benjamin Mainardi is an analyst at the Center for Maritime Strategy.