US, Ukrainian, and European officials reportedly agreed on unspecified security guarantees for Ukraine during a peace negotiation meeting in Berlin, Germany, on December 15. Ukrainian President Volodymyr Zelensky, Ukrainian Defense Council Secretary Rustem Umerov, US Special Envoy to the Middle East Steve Witkoff, and former Senior Advisor to the US President Jared Kushner met in Berlin, Germany, on December 15 to continue negotiations for a prospective peace deal to end Russia’s war in Ukraine.[1] Two US officials told the New York Times (NYT) on December 15 that the United States, Ukraine, and Europe agreed on a “NATO-like” security guarantee for the future security of Ukraine.[2] The US officials stated that the majority of the December 14 to 15 negotiations pertained to security guarantees, although the officials did not elaborate on specifics. The Kremlin has consistently indicated that it will reject any peace deals that offer reliable security guarantees for Ukraine, and is highly unlikely to accept a settlement that contains any provisions safeguarding Ukrainian territorial integrity.[3] The Kremlin notably effectively rejected the provision of reliable security guarantees for Ukraine as outlined in the US-proposed 28-point peace plan.[4]
Zelensky stated on December 15 that discussions concerning territorial issues are ongoing, and the two US officials cited by NYT reported that Zelensky and Russian President Vladimir Putin will likely need to discuss and decide upon the matter of territorial agreements themselves.[5] Putin has consistently declined to meet with Zelensky, including during the lead up to the full scale invasion and during several subsequent iterations of peace negotiations.[6] Russia has previously attempted to secure untenable territorial concessions from Ukraine that include Ukraine’s Fortress Belt, the fortified defensive line in Donetsk Oblast that has served as the backbone of Ukraine’s defenses since 2014.[7] Ukraine’s concession of its most valuable defense line into the hands of the Kremlin would provide Russia with more advantageous positions to renew aggression against southwestern and central Ukraine in the future.[8] ISW continues to assess that Russia will use political and military means to achieve its stated goal of seizing all of Ukraine and that Russia is therefore unlikely to accept a peace deal or security guarantees that do not grant full Russian control of Ukraine in the intermediate to long term future.[9]
Ukrainian forces conducted an unmanned underwater vehicle (UUV) strike against a Russian submarine for the first time in naval history on the night of December 14 to 15. The Ukrainian Security Service (SBU) published footage on December 15, which was later geolocated, showing Ukrainian “Sub Sea Baby” UUVs strike a Russian Project 636 Varshavyanka-class (NATO Kilo-class) submarine docked at the Novorossiysk Naval Base in Krasnodar Krai, causing explosions and critical damage to the submarine.[10] The SBU noted that the submarine was equipped with four Kalibr cruise missile launchers that Russia used to strike Ukraine and that the damage may have forced Russian forces to stop operating the submarine. Planet Labs satellite imagery captured on December 5 shows that two Kilo-class submarines were present at the Novorossiysk Naval Base as of December 5, and lower-resolution imagery captured on December 11 indicates that at least one Kilo-class submarine was present at the base as of December 11. National Aeronautics and Space Administration Fire Information for Resource Management System (NASA FIRMS) data published on December 15 indicates that there were fires near the Novorossiysk Naval Base.[11] Russian forces previously docked Kilo-class submarines in occupied Crimea and the Sevastopol port but began withdrawing them from the western Black Sea and transferring them to Novorossiysk in October 2023 due to a successful Ukrainian strike campaign against Russian Black Sea Fleet assets.[12] Russia uses Kilo-class submarines to conduct Kalibr cruise missile strikes against Ukraine, primarily Odesa Oblast, and the Ukrainian strike likely intended to degrade Russia’s ability to target Odesa Oblast with Kalibr missiles. Ukraine’s strike against the Kilo-class submarine in Novorossiysk shows that Ukrainian forces continue to modernize and optimize their unmanned capabilities such that Ukraine can strike Russian military targets at a range that Russian forces previously thought safe.
Russian forces are striking Ukrainian logistics lines in Odesa Oblast with various air launched munitions, including glide bombs, highlighting Ukraine’s urgent need for a well provisioned and diverse air defense umbrella. Geolocated footage published on December 15 shows Russian long range drones and glide bombs striking a bridge on the P-70 Odesa City- Bilhorod-Dnistrovskyi highway over the Dneister River in Zatoka, Odesa Oblast, on December 14.[20] Russian milbloggers claimed on December 14 that Russian forces struck a railway bridge near Zatoka with glide bombs and Geran (Shahed) drones, and a Kremlin-affiliated milblogger claimed on December 15 that the Russian strikes completely destroyed the bridge.[21] Additional geolocated footage published on December 15 shows Russian drones striking the Odeska railway bridge over the Sarata River in southern Sarata, Odesa Oblast.[22] Russian forces have recently intensified strikes against Odesa Oblast in parallel with intensified Kremlin rhetorical threats.[23] The Russian use of glide bombs as part of their strike packages against Odesa Oblast is notable, as they allow Russian forces to cause damage to Ukrainian logistical infrastructure with relatively cheaper munitions.[24] Russian forces must still use expensive manned aircraft to launch these glide bombs, which makes the aircraft vulnerable to the threat of Ukrainian air defenses, forcing Russia to weigh the balance of using cheaper munitions at the expense of its more exquisite aircraft systems. The increase in guided glide bomb attacks against Odesa Oblast highlights the fact that Ukraine urgently needs a holistic air defense umbrella that allows it to down manned aircraft, missiles, and drones alike.
Russian forces launched 9,298 drones and 270 missiles in October 2025, 5,444 drones and 216 missiles in November 2025, and 2,757 drones and 91 missiles in December 2025 as of December 15.[28] ISW has previously observed reports that Russian forces are engaging in a large-scale strike campaign that targets one or two specific regions in quick succession to degrade Ukraine’s ability to repair energy infrastructure rapidly.[29] Russian forces also focus on targeting different elements of Ukraine’s energy infrastructure, including substations, to systematically destroy the entire Ukrainian energy ecosystem and complicate Ukraine’s ability to treat targeted areas, elongating periods without power.[30] ISW continues to assess that Russia‘s increasingly large strike packages highlight the critical importance of Western assistance in bolstering Ukraine’s air defense capabilities, particularly with subsidies for Ukrainian programs that focus on air defense innovations such as Ukraine’s drone interceptor programs.
Key Takeaways
- US, Ukrainian, and European officials reportedly agreed on unspecified security guarantees for Ukraine during a peace negotiation meeting in Berlin, Germany, on December 15.
- Ukrainian forces conducted an unmanned underwater vehicle (UUV) strike against a Russian submarine for the first time in naval history on the night of December 14 to 15.
- Ukrainian forces continue counterattacking in the Kupyansk direction as Russian ultranationalist milbloggers acknowledge the severity of the situation for Russian forces.
- Russian forces are striking Ukrainian logistics lines in Odesa Oblast with various air launched munitions, including glide bombs, highlighting Ukraine’s urgent need for a well provisioned and diverse air defense umbrella.
- Russian strikes appear to be advancing the Kremlin’s stated goal of degrading Ukraine’s energy infrastructure by splitting Ukraine’s power grid in half. Ukraine requires Western-provided air defense systems and partner support for its drone interceptor development to safeguard itself against increasingly devastating strikes on its energy infrastructure.
- Ukrainian forces recently advanced in western Zaporizhia Oblast. Russian forces recently advanced in the Kostyantynivka-Druzhkivka tactical area.