ATHENS — The considerable fanfare surrounding a fresh round of peace talks between Russia and Ukraine at Istanbul yesterday risks fizzling fast — and if you are among the thousands still trapped in the besieged Ukrainian city (at least for the moment) of Mariupol, it probably already has. 

That is because the real power broker in this mess, Vladimir Putin, has shot down an incipient humanitarian aid mission to the city that forces under his command have largely destroyed. The idea for said mission started with a Greek proposal, to which France glommed on and Turkey too, but Mr. Putin reportedly told President Macron in another of their lengthy phone chats that Ukrainian forces still fighting in Mariupol would have to surrender before humanitarian aid can be dispatched, the Greek daily Kathimerini reported this morning. 

Ukrainian fighters laying down their arms is little more than a pipe dream for Mr. Putin, who for his part appears to be throwing more mettle into the fight he started, its provenance be damned. Russian state media reported that a Chechen warlord accused of multiple human rights abuses, Ramzan Kadyrov, has traveled to Mariupol to continue the Kremlin’s brutal onslaught of the strategic port city. According to the Times of London, the 45-year-old Mr. Kadyrov is notorious for torturing his critics in the tightly controlled Muslim republic he rules in the south of Russia. 

Mr. Kadyrov has been one of Mr. Putin’s principal cheerleaders for the war in Ukraine, the paper reports, has mocked Ukraine’s president, Volodymyr Zelensky, has taunted Elon Musk on Twitter, and has a penchant for wearing pricey Prada boots. If some of that has a surreal ring to it, the hard facts are that thousands of civilians have likely been killed in Mariupol since bombing began four weeks ago, as the head of the UN human rights mission told Reuters on Tuesday. 

That nobody was poisoned at the Turkey peace talks yesterday could be seen as a sign of a hopeful new trend in Russian hospitality, though it was the Turkish president, Tayyip Erdoğan, who formally hosted them. Ukraine’s foreign minister, Dmytro Kuleba, previously advised anyone taking part in negotiations not to eat or drink anything during the process and during Tuesday’s session delegates were given bottled water with glasses covered with paper tops. 

The warning was apparently prompted by reports that the peripatetic Russian-Israeli oligarch Roman Abramovich, who was on hand in an unofficial capacity, had been poisoned by chocolate at a round of peace talks earlier this month at Kiev.

Following this round, the leader of President Zelensky’s faction in parliament and head of the delegation that Kiev dispatched to Istanbul, David Arakhamia, said Ukraine wants security guarantees that are stronger than NATO’s Article 5, which commits each member state to consider an armed attack against one member state to be an armed attack against them all. “We insist that this should be an agreement on security guarantees signed and ratified [by parliaments] to avoid repeating the mistake of the Budapest Memorandum,” Mr. Arakhamia said. 

As the Kyiv Independent noted, under the non-binding 1994 Budapest Memorandum, Russia, America, and the U.K. pledged not to use military force against Ukraine in exchange for it renouncing the nuclear weapons it had obtained from the Soviet Union. 

Russia violated the memorandum by invading Ukraine in 2014-2022, and other guarantor countries failed to protect Ukraine.  Mr. Arakhamia said that under the guarantees proposed by Ukraine on March 29, guarantor countries must consult each other within three days after the beginning of military aggression or hybrid war. How Moscow will respond to all this, if it responds at all, is anybody’s guess.

Amid escalating international intrigue — Belgium, the Netherlands and Ireland on Tuesday expelled dozens of Russian diplomats, many for alleged spying — the situation on the ground in Ukraine remains muddled at best and is simply dire in many spots. Not just Mariupol. 

Things are very rough in the city of Izyum, on the Donets River in eastern Ukraine’s Kharkiv Oblast.  A deputy in the Izyum city council’s office, Max Strelnyk, says the city has not received a humanitarian convoy since March 14. Mr. Strelnyk told CNN that there’s been no letup in the bombing and that while Russia claims “that they will decrease military operations in the Kyiv and Chernihiv oblasts, Izyum and the greater Kharkiv region will have no such luck.”

Underscoring that assertion, a Russian presidential aide, Vladimir Medinsky, said that Tuesday’s announcement of plans for a de-escalation by the Russian military around Kiev and Chernihiv “is not a ceasefire.” In remarks to Russian state-owned channel RT, Mr. Medinsky said the first step agreed by Russia in talks with Ukraine “concerns a gradual military de-escalation in two main directions — Kyiv and Chernihiv,” adding, “We understand that there are people in Kiev who need to make decisions, so we do not want to expose this city to additional risk.” 

In the meantime, the Kyiv Independent reported that air raid sirens sounded early in the morning of March 30 in several oblasts across Ukraine, including Zhytomyr, Kharkiv, Dnipro, Poltava — and Kiev.