The British Ministry of Defense posted on Twitter early Monday morning that more than a quarter of the 120-member tactical groups that Russia has committed to in the conflict have “become militarily ineffective” and that the nation’s most select forces “have suffered the highest level of deterioration.” . “The 120-battalion teams represented about 65 percent of the country’s ground combat force at the beginning of the invasion. The news is the latest sign that Russia has struggled to maintain momentum during the invasion. Some experts initially believed that Russia could quickly occupy Ukraine, but after two months of fighting, Ukraine continues to push Russian troops. The ministry specifically noted that the Russian air force, VDV, had suffered significant losses since the invasion began in late February. The ministry did not specify how its information was obtained. Some of Russia’s most select military units will be weakened for years, the British Ministry of Defense said on Monday. Above, Russian military probationers appear in St. Petersburg, Russia, on April 28. OLGA MALTSEVA / AFP via Getty Images “It will probably take years for Russia to rebuild these forces,” the ministry wrote. Ukraine’s Defense Ministry claimed Monday that Russia had lost 23,800 troops. Ukraine also had 1,048 tanks, 2,519 armored personnel carriers, 459 artillery pieces, 194 aircraft and 84 cruise missiles in Russia’s losses. At the end of March, NATO estimated that Russia had lost between 7,000 and 15,000 troops. Ukraine says up to 3,000 Ukrainian soldiers have been killed in the war, CNN reported. However, this number has not been independently verified. On Monday, Chief of General Staff of Ukraine Valeriy Zaluzhniy claimed that a Ukrainian drone had destroyed two Russian Raptor-class patrol cars near Snake Island in the Black Sea. Ukraine’s Defense Ministry also said Monday that Russia was “intensifying” a campaign to recruit new military volunteers to replace the number of troops it has lost since the invasion began. However, he noted that the recruitment did not take place in Moscow, Russia’s largest city. “Campaign events are being held to motivate ‘volunteers’ to serve. In particular, traditional Russian narratives of the ‘collective West’ and ‘non-existent Ukraine’ are being repeated. They also promise increased material security and benefits,” an English translation read. There have also been recent signs of morale among both the military and the Russian population. A poll released last Thursday found that amid heavy losses, support for the conflict has fallen. The poll found that 74 percent of those polled said they supported the Russian military — less than 81 percent in March. However, as Russian casualties continue to rise, the threat of Russian use of nuclear weapons continues to grow, Senator Bob Menendez, chairman of the Senate Foreign Relations Committee, said during an appearance on Fox Newsover over the weekend. “Well, one of my concerns is that, ironically, the more successful the Ukrainians are, the greater the risk that Putin will do something because he loses and has to save face at home,” Menendez said. Newsweek contacted the Russian Foreign Ministry for comment.