Assessed Control of Terrain, Russo-Ukrainian War, 4 June 2026 at 13:30 ET. Map: Institute for the Study of War and AEI’s Critical Threats Project. All rights reserved.

The Office of the President of Ukraine released the letter at approximately 21:55 local time on 4 June. It was addressed formally to the President of the Russian Federation. The timing was deliberate: Ukrainian drones had struck the St. Petersburg oil terminal and the Russian Baltic Fleet corvette Boikiy at Kronstadt the previous morning, the day Putin opened SPIEF. Zelensky published the letter as that forum continued.

The core offer was an immediate ceasefire along the current frontline, a face-to-face bilateral summit in a neutral country, a full prisoner exchange as an opening act, and European and American participation in any formal talks that followed. Zelensky proposed Istanbul, the Vatican, or Switzerland as venues. He offered to meet as early as 5 June if Russia agreed to a ceasefire before the leaders’ meeting, or to set a fixed later date if it did not. American monitoring and mediation guarantees were named as conditions for any ceasefire period to hold.

The letter ran significantly longer than a diplomatic aide-memoire. Zelensky argued that nearly 13 of Putin’s 26 years in power had been spent in war against Ukraine. He cited Russian losses of over 30,000 troops in the preceding period and told Putin that Moscow lacked the financial resources to sustain indefinite domestic loyalty-buying. He warned that he had seen intelligence suggesting Russia was planning to continue the war into 2027 and 2028, and that Belarus was being drawn deeper into the conflict alongside preparations around Transnistria. “If you do not personally come to the conclusion that it is time to end this war,” he wrote, “Ukraine will continue fighting for its existence.”

The Kremlin responded the same evening. Peskov told state media that Putin had not yet been shown the letter but that Zelensky could come to Moscow “any time.” Putin’s position has been consistent since 2022: he will meet Zelensky to ratify an agreement already settled through intermediaries, not to negotiate one. He has not accepted a neutral venue. Direct addresses from Zelensky to Putin are rare; the gap since Russia’s full-scale invasion began in February 2022 is now more than four years, and months of United States-led shuttle diplomacy have not moved the parties toward an agreed framework.

The morning of 3 June was chosen carefully. As the first delegates arrived for the St. Petersburg International Economic Forum, Ukrainian drones hit the St. Petersburg oil terminal in Leningrad Oblast, one of the largest oil transshipment complexes on the Baltic Sea, and struck the corvette Boikiy in dry dock at the Kronstadt naval base. Zelensky confirmed both strikes on social media. Leningrad Oblast Governor Aleksandr Drozdenko said 50 drones were shot down over the region but did not address the terminal fires. Photographs distributed on the forum’s opening day showed SPIEF branding against a curtain of black smoke.

The drones covered more than 1,000 kilometres from the Ukrainian border, the same basic capability that has been striking oil refineries and logistics hubs across the Russian rear since March. ISW noted that the SPIEF attack extended a pattern of Ukrainian strikes on Russian oil and gas infrastructure and specifically contradicted the Kremlin’s preferred framing of the forum as a platform for projecting economic stability. Separately, CNN reported that two firefighters died at the oil terminal fire, attributed by regional authorities to debris from an intercepted drone. Pulkovo Airport delayed nearly 30 flights and diverted nine others. Putin had pruned the Victory Day parade in Moscow weeks earlier for fear of Ukrainian drone attacks; the SPIEF fire produced a similar result without requiring any alteration of the public programme.

On 4 June, the ISW assessment noted that Russian officials continued to ignore domestic economic problems at the forum. Ukrainian intelligence estimated that Russia was attempting to conceal an $80 billion budget deficit, that revenues had fallen by 40 per cent, and that 71 of Russia’s regions were running deficits. Fuel shortages, rising diesel prices, and coupon-based rationing have been reported in multiple regions, including Crimea. The forum continued to present a narrative of growth and stability. Independent economic commentary, including from Sberbank chief executive Herman Gref and Severstal owner Alexei Mordashov, indicated that ruble weakening and inflationary pressure were effectively unavoidable from their perspective inside the forum itself.

ISW confirmed no advances by either Russian or Ukrainian forces across the theatre on 4 June. On the overnight of 3 to 4 June, Russian forces launched 293 drones and one Iskander-M ballistic missile against Ukraine. The Ukrainian Air Force intercepted 264 of the 293 drones; 24 drones struck 11 locations, and falling debris was recorded at 12 sites. Russian strikes hit the Kherson region, Konotop in Sumy Oblast, and a critical infrastructure facility in Odesa Oblast, among other targets. The Kyiv region also saw strikes, with a fuel truck driver injured in an aerial attack.

On 4 June, Ukrainian forces continued their own long-range campaign. Targets struck inside Russia included a double strike on an oil depot in Pereyaslav in the Kyiv Region, energy facilities in Sarny and Lebedyn, and a locomotive depot in Snovsk as well as a seaport facility. Ukraine’s Unmanned Systems Forces Commander Robert Brovdi confirmed the hit on Boikiy at Kronstadt as part of the 3 June operation. A Russian Svetlyak-class border patrol ship in occupied Crimea was also reported struck in operations conducted on 3 and 4 June, per Ukrinform citing Ukrainian military reporting.

Russian casualty figures remain contested. Ukrainian military estimates put total Russian personnel losses since February 2022 at approximately 1,369,340, including roughly 1,300 killed or wounded in the 24 hours to 4 June. These figures are Ukrainian government reporting and are not independently verifiable. ISW also noted the Russian MoD’s demonstration of a new battle management information system, assessed as intended for deployment with international exercise partners during Center 2026, the strategic command-and-staff exercise scheduled for September. The system’s current operational status in Ukraine was not detailed in open sources.

On 3 to 4 June, Hungary’s new Prime Minister Peter Magyar announced a comprehensive agreement with Kyiv on the expansion of linguistic, educational, cultural, and political rights for the ethnic Hungarian minority in Transcarpathia, effectively ending Budapest’s two-year block on Ukraine’s EU accession process. All 27 EU member states subsequently cleared the opening of Cluster 1 negotiations, the so-called Fundamentals cluster, with the Cypriot EU presidency expected to formally open the first chapters in mid-June. Ukraine’s Prime Minister Yuliia Svyrydenko confirmed the agreement on 4 June. The Hungarian-Ukrainian deal also followed Magyar’s government lifting Orban-era vetoes on European Peace Facility military reimbursements totalling 6.6 billion euros and reaching a separate agreement with the European Commission on 16.4 billion euros in previously frozen EU funds.

The EU accession development sits outside the frontline but carries strategic weight. Kyiv has treated the accession path as part of the broader argument that Ukraine’s future lies in Western institutions regardless of how the war ends. The accession opening coincides with the US House of Representatives passing the Ukraine Support Act, which allocated $8 billion in military financing and extended the Ukraine Security Assistance Initiative through 2027 while imposing additional sanctions on Russia. The bill passed as a rebuke to the White House’s posture on Russia policy, per Kyiv Post’s characterisation of the vote.

Against all of that, the Zelensky letter and Kremlin response on 4 June changed nothing on the ground. The letter was addressed to a leader who has told foreign mediators he expects to finalise terms, not negotiate them. Trump said a direct Putin-Zelensky meeting would be “great” but pushed both sides to compromise; no mechanism for compelling either side toward the Zelensky-proposed format is visible in the current diplomatic landscape. The strikes, the drones, and the frontline stalemate continued through the day and overnight.