Hard Red Lines and Fragile Guarantees The Russia–Ukraine War: Diplomacy, Battlefield Reality, and the Limits of Peace (December 2025)

Executive Summary

Renewed diplomatic momentum surrounding the Russia–Ukraine war has emerged following high-level negotiations in Berlin involving Ukraine, the United States, and key European powers. These talks produced a preliminary framework addressing security guarantees, post-war enforcement mechanisms, and long-term reconstruction funding for Ukraine. U.S. President Donald Trump has publicly expressed optimism, claiming that peace talks are “closer than ever.”

However, this diplomatic progress stands in sharp contrast to political and military realities. Russia has drawn a firm “red line” on territorial issues, insisting that Crimea and four other Ukrainian regions are non-negotiable. Ukraine, while showing flexibility on NATO membership, remains resolute that occupied territories cannot be legally surrendered without binding security guarantees. Meanwhile, fighting on the ground continues, with Russia claiming new territorial gains. The result is a widening gap between diplomatic ambition and strategic reality.

The Berlin Talks: Progress Without Resolution

The December 2025 Berlin negotiations marked a shift from abstract diplomacy to concrete political and security planning. For the first time, Western partners outlined operational mechanisms rather than vague assurances.

Key elements discussed included:

• Article 5-like security guarantees for Ukraine from a coalition of Western states
• A European-led multinational peace enforcement force
• U.S.-led ceasefire monitoring and intelligence coordination
• Long-term reconstruction financing, potentially involving frozen Russian assets

Ukraine signalled willingness to de-prioritise NATO membership if these security guarantees were credible and enforceable. This represented a significant diplomatic concession aimed at removing one of Moscow’s long-standing objections.

Yet the talks failed to bridge the central divide: territory. No progress was made on reconciling Russia’s annexation claims with Ukraine’s insistence on sovereignty.

Berlin’s achievement lay in institutional design.
Berlin’s failure was its inability to overcome the war’s core political contradiction.

Russia’s Position: Territory as a Non-Negotiable Red Line

Russia’s stance has been explicit and uncompromising. Deputy Foreign Minister Sergei Ryabkov reiterated that Crimea, Donetsk, Luhansk, Kherson, and Zaporizhzhia are regarded by Moscow as permanently Russian territory.

Russia’s conditions include:

• Absolute rejection of any territorial compromise
• Opposition to NATO presence or Western peacekeepers on Ukrainian soil
• Rejection of temporary ceasefires, which Moscow claims only allow Ukraine time to rearm
• Demand for a comprehensive settlement recognising Russia’s strategic interests

This is not rhetorical posturing. It represents Russia’s negotiating floor, limiting how far its diplomats can move even under international pressure.

From Moscow’s perspective, relinquishing territorial claims would undermine domestic legitimacy and weaken its strategic buffer against the West.

Ukraine’s Red Lines: Sovereignty and Security Guarantees

President Volodymyr Zelenskyy has adopted a dual-track strategy: diplomatic flexibility combined with firm political limits.

Ukraine’s core principles are:

• No legal surrender of occupied territory
• Willingness to discuss alternatives to NATO membership
• Absolute insistence on binding security guarantees before any political concessions

For Kyiv, territorial integrity is not merely symbolic. It is tied to:

• National survival
• Constitutional legality
• Domestic political legitimacy

Any agreement perceived as trading land for promises would risk internal destabilisation and loss of public trust. Zelenskyy’s position reflects a hard political reality: peace without security is not peace, but postponement.

The United States and Trump’s Diplomatic Push

President Donald Trump has taken an unusually direct role in shaping the peace process, publicly stating that a deal is closer than at any previous stage of the war.

The U.S. approach is characterised by:

• Urgency and deal-making pragmatism
• Emphasis on negotiated trade-offs
• Pressure on all sides to reach closure

While this has injected momentum into stalled diplomacy, it has also raised concerns among European partners and Ukrainian officials. A rapid settlement lacking strong enforcement mechanisms could collapse under renewed Russian pressure, undermining Washington’s credibility as a guarantor.

The central risk is speed over substance.

What Do “Article 5-Like” Guarantees Really Mean?

The proposed security framework consists of three interlinked pillars:

• Legally binding defence commitments by a coalition of states, defining clear responses to renewed aggression
• A European-led multinational force deployed to enforce ceasefire lines and deter violations
• U.S. intelligence, surveillance, and verification systems to monitor compliance in real time

German Chancellor Friedrich Merz acknowledged that peacekeepers could be authorised to repel violations militarily — a significant shift from earlier European caution.

Russia, however, has categorically rejected any arrangement involving foreign troops with enforcement authority, viewing it as incompatible with its security objectives.

The Battlefield Reality: Diplomacy Under Fire

While negotiations continue, the war does not pause.
Russia claims:

• Advances in eastern Ukraine
• Pressure on strategic axes near logistics hubs and river crossings
• Expanded drone and artillery operations

Ukraine disputes several of these claims, but the overall trend is clear: military pressure is shaping diplomatic leverage.

Any ceasefire imposed under battlefield imbalance risks freezing gains in place — a reality that explains Ukraine’s insistence on enforcement mechanisms and Russia’s resistance to them.

Internal Ukrainian Risks: Zaluzhny’s Warning

Former Ukrainian Armed Forces Commander Valeriy Zaluzhny has issued a stark warning about the post-war period.

Key concerns include:

• The return of nearly one million combat veterans
• Insufficient employment, housing, and reintegration programs
• Rising draft evasion and desertion during the war

Without comprehensive reintegration planning, Ukraine could face:

• Social unrest
• Political fragmentation
• Even the risk of internal conflict

This highlights a critical truth: external peace guarantees are meaningless without internal stability.

Reconstruction and the Frozen Assets Debate

European governments are debating the use of frozen Russian state assets to finance Ukraine’s recovery through reparations-linked loans.

Advantages:

• Reduces burden on European taxpayers
• Links accountability to reconstruction

Challenges:

• Legal complexity
• Political resistance within the EU
• Risk-sharing disputes among member states

Regardless of the mechanism chosen, reconstruction will require hundreds of billions of euros and sustained international commitment well into the 2030s.

Possible Scenarios Ahead

• Security-first agreement without territorial recognition
– Ukraine retains legal sovereignty; enforcement mechanisms deter renewed war
• Weak ceasefire
– Temporary pause followed by renewed fighting
• Territorial concession deal
– Politically destabilising for Ukraine; unlikely to endure
• Diplomatic collapse
– Prolonged war and intensified confrontation

Each path carries significant risks — not only for Ukraine, but for European and global security.

Conclusion: Peace Without Guarantees Will Not Last

The Russia–Ukraine war has reached a moment of diplomatic possibility, but not resolution. Russia’s refusal to compromise on territory, Ukraine’s insistence on sovereignty, and the continuation of battlefield violence define the limits of the current peace effort.

A durable settlement requires:

• Binding legal security guarantees
• Credible military enforcement
• Long-term economic and social reconstruction
• Domestic political legitimacy within Ukraine

Any agreement lacking these foundations will merely freeze the conflict, not end it.

Peace without security is not peace — it is an intermission.