Russia’s Western Aggression Pathways: Baltic or Danube Corridor?
The brief assesses Russia’s strategic options for continued westward aggression, concluding that the Danube Mouth axis represents the most rewarding, probable, and operationally realistic path. Since 2022, the US has strengthened its security posture in Romania, recognizing the region's strategic vulnerability, while the EU maintains its conflict-averse posture, emphasizing negotiation over deterrence[1].
[1]The paper develops on earlier: Moldova’s Sustainable Transnistria Settlement (2024), Hybrid Threats:Implications for Moldova (2014, 2021), Russia potential for the military aggression in Bugeac against Ukraine and Moldova (2022).
1. Comparative Strategic Options: Baltics vs. Danube Mouth
Russia's strategic intent in westward aggression can follow two operational axes. The Northern Axis would likely focus on direct destabilization of the Baltic states (Estonia, Latvia) or potentially aggression directed against Lithuania from both Kaliningrad and Belarus. The Southern Axis would focus on hybrid and military operations targeting the Danube mouth – aiming at Romania's Danube-Black Sea frontier - and intrinsically parts of southern Ukraine, and southern Moldova with the Transnistria and Bugeac triangle assets. Factors influencing Moscow’s decisions include Russia’s implicit strengths and assets along with the exploitation of the region’s weaknesses. The adversarial intensity risk involved is a discouraging factor in the aggression pathways analysis evidenced by Russian most “resultative” occupation actions and dominant Russian military establishment tactics.
Each route presents distinct military, political, and geopolitical considerations, including testing NATO's Article 5 but also against the background of the region’s vulnerabilities and weaknesses to resist. The route options can be also viewed from several vantage points: economic emboldening, geopolitical influence, security and military defense gains. The Baltic Axis offers limited territorial or maritime gains but would undoubtedly trigger NATO’s collective defense clause (Article 5) due to the immediate nature of the aggression against NATO members. This makes it a high-risk strategy for Russia, likely resulting in direct military retaliation and political isolation. The local populations in the Baltics are largely hostile to Russia, leaving minimal room for societal leverage or proxy manipulation.
Comparing Options: Russia’s Western Axis Scenarios
On the contrary, the Danube Mouth Axis —particularly when approached through Moldova via Transnistria and Chitcani venue —presents a more plausible and less immediately escalatory path. It enables Russia to operate in the grey zone, leveraging plausible deniability and local proxies to delay or complicate a NATO response. This approach is well documented in Russia’s past operations and promises tangible strategic gains: potential control over the Bugeac region, disruption of critical grain and energy routes, and the possibility to deny maritime access through the Black Sea and Danube corridor. Moldova’s non-NATO and declared neutrality status, coupled with fragmented internal and societal landscape as well as sizable pro-Russian loyalty particularly in the Bugac but also beyond offer exploitable opportunities to mask aggression as internal instability rather than foreign invasion.
From a conventional military standpoint, the Danube Mouth axis presents a more feasible and sustainable option for Russian operations. The Baltic region is heavily reinforced by NATO forces, with integrated air defense systems, forward-deployed battlegroups (Germany, Poland, UK), and rapid reinforcement protocols, making any Russian advance there susceptible to decisive counteraction. In contrast, the southeastern flank, lacks comparable force concentration and terrain-adapted defense and a more permissive battlespace with weaker resistance. Russian military establishment implementers (Gerasimov Doctrine) tend to favor scalable, hybrid to conventional operations that build on prior localized successes, rather than initiating high-risk, high-cost conventional confrontations upfront. This reflects a learned lesson from the Ukraine invasion: that targeting a better-prepared, conventionally capable adversary early in the campaign was a misstep. The Russian military establishment preference is to target the less-defended periphery, where conventional forces can establish footholds with manageable escalation risks and more sustainable logistics.
The presence or absence of Türkiye as a player shifts the risk calculus. Türkiye is a gatekeeper to the Black Sea under the Montreux Convention; however, its role is limited to a maritime defense posture and Ankara opposes any other territorial defense roles outside its core interests. Without Turkish engagement, Russia's freedom to operate in the Black Sea and along the Danube increases.
Assessment
The Baltic Axis is a high-risk, high-impact strike likely to escalate into direct confrontation; this will considerably unify NATO European countries, raising Russia’s costs and isolation. The Danube Mouth Axis, exploiting Moldova using Transnistria as a means of aiming at Bugeac, allows phased escalation, plausible deniability, and strategic gains without directly breaching NATO territory initially. While both axes remain theoretically viable for projecting aggression westward, the Danube Mouth presents a more probable, advantageous, and strategically fluid option for Russia. It allows for tactical exploitation of regional weaknesses, testing of NATO cohesion, and the pursuit of territorial and economic objectives—all without immediately triggering Article 5.
2. Danube Mouth Option: Transnistria & Bugeac
The southern corridor option involves a phased campaign using Transnistria as a springboard—not as a final objective given terrain and geography. The goal is to infiltrate and secure Moldova’s and Ukraine’s southern region (Bugeac), using societal divisions and Moldovan declared neutrality, to stage operations threatening the Danube and ultimately Romania’s southeastern flank establishing a firm (Kaliningrad type) footprint on the North-West Black Sea shore at a minimum.
Moldovan Neutrality & Weakness, Transnistria's Role
Transnistria functions as a de facto forward-operating base for Russia, hosting approximately 2,000 regular Russian troops and commanding an estimated 15,000 Transnistria-based infantry forces under effective Russian control. Its military utility is reinforced by Soviet-era infrastructure, including the region’s largest ammunition depot, an operational airstrip, and an estimated mobilization pool of up to 40,000 personnel. Geographically, the Chițcani bridgehead lies less than 50 kilometers from Moldova’s Bugeac, offering a direct and rapidly exploitable corridor into the southern theater of operations as hundreds of years of military history proves.
Moldova is politically fragmented and militarily unprepared for any hybrid infiltration. Its initially Russian-dictated and later self-imposed neutrality precludes a NATO role. Decision-makers in Moldova prioritize power holding at any cost and mirror EU status-quo and negotiation only blueprint in assessing and approaching the situation. The broader Bugeac region—spanning southern Moldova and southwestern Ukraine—is home to around 500,000 inhabitants, with a potential recruitment pool of up to 100,000 individuals, including an estimated 5,000 military-minded security agents, former policemen and others who could be mobilized swiftly in a crisis scenario. The region includes two military-capable airfields and several small ports, embedded within terrain that favors defensive operations. Moldova’s Bugeac is in administrative and ideological confrontation with the central authorities in Chișinău,whichenhances the feasibility of hybrid subversion.
Campaign Phases
Assessment
The Danube Mouth campaign provides Russia with a scalable, asymmetric offensive platform that can remain below NATO’s immediate threshold of Article 5 engagement. Transnistria is not a war objective but a force multiplier, enabling strategic encroachment into southern Moldova and Ukraine. The exploitation of local demographics and administrative divisions—especially in Bugeac—creates a soft front for infiltration. Success would yield territorial continuity, capture of maritime Middle Corridor transportation and energy corridors, and shift Black Sea control dynamics. Critically, it would establish a “Reverse Suwalki Gap”: a wedge between Ukraine and NATO, pressuring Romania from the east and further isolating Moldova geopolitically. This outcome would fracture NATO’s southeastern flank, degrade EU logistics, and permanently alter the balance in the Black Sea basin.
3. Euro-Atlantic Posture
In May 2025, the EU launched its first coherent Black Sea Strategy, outlining three key objectives: enhancing security and stability, fostering growth and prosperity, and promoting environmental protection. While symbolic, the strategy reflects a status-quo-oriented, incrementalism approach. Signed by the new High Representative but crafted by the previous EU External Service leadership, it reflects the latest strategy for the region. It capitalizes on the previous sectoral strategies (maritime, energy, infrastructure via Europe Gateway) and incorporates hybrid threat recognition and demining support, promotion of the peace-making and negotiation formats for conflict-resolution, but lacks prioritization or decisive scenario planning.
Romania, Poland and Bulgaria as well as Lithuania and other Baltic countries opt for micro-acting following the EU canvas. Despite their direct regional stakes and the potentially high security costs of inaction, these countries have not assumed the proactive regional leadership role. Their engagement often materializes as isolated initiatives within NATO frameworks or few efforts within EU mechanisms. Overall, the EU’s posture remains reactive, fragmented across its external action tools. The document deliberately avoids confronting the most pressing threats—such as the militarized status of occupied Transnistria—and instead adopts a posture that accommodates all possible scenarios without steering toward preferred or strategic outcomes. It relies on a preference for mediation and dialogue, particularly regarding unresolved conflicts like Transnistria.
Following a reassessment of its prior policy, the U.S. Congress passed the 2023 Black Sea Strategy Act, emphasizing: Security augmentation (Constanța military base), Sanctions enforcement, Support for the Middle Corridor as an alternative to Russian trade routes. The U.S. has reinforced its strategic assets in Romania, including: expansion of Constanța Air Base, backing Romania’s increase from 2% to 3% of GDP in defense spending,military deployments: the U.S. and France lead a brigade-sized NATO presence in Romania, Italy does the same in Bulgaria.
NATO’s defensive architecture develops with Romania as a key country given that it already meets the 2% threshold and has pledged 3%. Türkiye is focused on defense of the Bosphorus and Dardanelles, with Bulgaria having limited capabilities. For air and missile defense, NATO has deployed Patriot missile systems and maintains continuous air policing missions across Romanian and Bulgarian airspace with rapid detection and interception capability. On land, forward-deployed NATO battlegroups are stationed in Romania and Bulgaria. These forces are supported by reinforcement mechanisms in the event of escalation.
In Moldova, the votes of the diaspora based in Western countries secured last year’s electoral win for pro-European President Maia Sandu. Moldova faces parliamentary elections in September 2025 with the president’s party - in power since 2021- at some 30%. The government pleads neutrality and negotiations, avoids complying with the EU sanctions regime against Russia and claims it faces refugee, energy, logistical and hybrid destabilization crises. In the event of a Russian Danube axis of aggression NATO is not prepared to stabilize the Bugeac region and is only prepared to contain and repel limited offensives into Romania proper. The realistic defensive line lies along the Danube–Galați–Constanța axis, given Romania’s geography, logistics via the Danube, and NATO's capacity for rapid reinforcement.
