The highly classified leaked Pentagon documents posted to social media offer a pessimistic US viewpoint about the state of the war in Ukraine, highlighting weaknesses in Ukraine’s weaponry and air defenses and predicting a stalemate in the war for months to come. The documents, which appear to date from February and March, detail many of Ukraine’s perceived military shortfalls as Kyiv prepares for a spring counteroffensive against Russia. Several of the classified documents warn that Ukraine’s medium-range air defenses to protect front-line troops will be “completely reduced by May 23,” suggesting Russia could soon have aerial superiority and Ukraine could lose the ability to amass ground forces in a counteroffensive. The documents also underscore lingering problems with Russia’s own military offensive, predicting that the result will be a stalemate between the two sides for the foreseeable future. “Russia’s grinding campaign of attrition in the Donbas region is likely heading toward a stalemate, thwarting Moscow’s goal to capture the entire region in 2023,” states one of the classified documents. Officials familiar with the situation tell CNN the documents appear to be part of a daily intelligence briefing deck prepared for the Pentagon’s senior leaders, including Chairman of the Joint Chiefs of Staff Gen. Mark Milley. The leaking of the documents, many of which are marked top secret, represents a major national security breach, and the Justice Department has launched a criminal investigation into who may have leaked them while the Pentagon is investigating how the leak impacts US national security. In addition to the assessment of the Ukraine war, the documents include intelligence gathered on allies and adversaries alike. Retired Lt. Gen. Mark Hertling, a CNN national security and military analyst, said that the challenges Ukraine faces with its planned counteroffensive have been clear for weeks, including the need to integrate new equipment and new troops and ensure that a sufficient supply chain is in place. He did not think that the document leak would alter Kyiv’s plans. “I haven’t seen anything in the documents I’ve seen that would cause me as a commander to change my plans,” Hertling said. “It’s given some information to the Russians in terms of unit locations and ammo and equipment capabilities, but I would venture to say the Russians already knew all that anyway.” US officials have warned publicly the war could drag on In many ways, the assessment of the Ukraine war is similar to what US officials have said publicly, as top Biden administration officials have said the conflict is likely to drag on for months, if not longer. But the detailed and unflinching assessment of the war is laid out starkly in the briefing slides about the challenges Ukraine faces despite its successes more than a year into the war. An official from a country part of the Five Eyes intelligence-sharing agreement with the US told CNN previously that it was alarming to see the leaked Ukraine war information handicapping the country on the battlefield. “Gains for Ukraine will be hard to accomplish, but it does not help to have the private US assessment pointing to a likely yearlong stalemate revealed publicly,” the official said. Publicly, US and Ukrainian officials have downplayed the significance of the classified documents. Secretary of State Antony Blinken has reassured Ukraine of the United States’ “ironclad” support for the country, following the Pentagon document leaks, according to Ukrainian Foreign Minister Dmytro Kuleba. During a call on Tuesday Blinken “reaffirmed the ironclad U.S. support and vehemently rejected any attempts to cast doubt on Ukraine’s capacity to win on the battlefield,” Kuleba wrote Tuesday on Twitter. “The U.S. remains Ukraine’s trustworthy partner, focused on advancing our victory and securing a just peace,” Kuleba said. At a press conference Tuesday, Defense Secretary Lloyd Austin that the department will “turn over every rock until we find the source” of the leaked intelligence documents. CNN has reviewed 53 leaked documents, all of which appear to have been produced between mid-February and early March. At least one of the documents appears to have been altered, CNN previously reported, which listed Russian and Ukrainian casualty numbers and more than halved the number of Russian deaths before being spread on pro-Russian Telegram channels. Still, US officials have acknowledged the bulk of the documents appear to be genuine. Ukraine has already altered some of its military plans because of the leak, a source close to Zelensky told CNN. “These documents are static. They’re a picture of a specific time. Both United States and Ukraine have the ability to modify what they’re doing and how they’re approaching this issue, and we certainly have plenty of time for Ukraine to do so,” House Intelligence Chairman Mike Turner told CNN’s Jake Tapper on Monday. Additional documents have also emerged. The Washington Post reported Monday on another leaked document with a bleak assessment from February that challenges with troops, ammunition and equipment could cause Ukraine to fall “well short” of its goals in its planned spring counteroffensive. A document from February states that the US assesses Ukraine can generate 12 combat brigades for the spring counteroffensive, including three trained in Ukraine and nine trained and equipped by the US. Six of the brigades would be ready by the end of March and the remaining six by the end of April, according to the document. The leaked documents include a detailed maps of battlefield positions, statistics on the number of troops killed and wounded and estimates of tanks, fighter jets and other weaponry that’s been fielded as well as destroyed. One slide provides a timeline for when Ukraine’s ground will be frozen, when it will be muddy and when it will be favorable to move through. There are assessments of Ukrainian forces around Bakhmut, where some of the fiercest fighting between the two sides has taken place this year. In one update in February, the intelligence assessment includes details on villages where Ukraine’s military had withdrawn and which positions it was still controlling.