Russian Defense Minister Shoigu reported to President Putin on the 21st that Russian forces have controlled other areas of Mariupol city except the Asian speed steel plant. Putin ordered the cancellation of the plan to attack the Asian speed steel plant on the same day and changed it to a blockade to prevent any armed personnel from escaping. Analysts believe that controlling Mariupol, a strategic town, is of great significance for Russia to achieve its operational objectives and promote a new stage of operations. Why did Russia cancel the strong attack plan Shoigu said that at present, more than 2000 armed personnel are "firmly" trapped in the Asian speed steel plant, and the strong attack takes three to four days. Putin ordered to cancel the attack and replace it with a blockade. Putin said that the purpose of canceling the strong attack is to protect the lives of Russian soldiers. In addition, Russia will ensure the safety of the lives of the surrendered Ukrainian army personnel and give them due treatment. Yasu iron and steel plant was built in the Soviet era. The industrial area has its own power supply and water supply system, as well as railways and overpasses. In order to resist the nuclear war, Yasu iron and steel plant has built a huge tunnel network, which is easy to defend but difficult to attack. According to the US veterans today website and other media reports, the tunnel has a total length of about 24 kilometers, a maximum depth of 30 meters and a depth of 6 floors, which is difficult to blow up from the ground. In addition, it is convenient for the Ukrainian army to transfer, use underground communication equipment to contact and organize ambushes from different entrances and exits. Yang Zhen, deputy director of the Northeast Asia Research Center of the Shanghai Academy of political science and law and a military expert, believes that there are multiple considerations for the Russian army to change to a blockade. It is a complete fortification to avoid major casualties to the Russian army. Second, we hope to arrest foreign mercenaries and even NATO military personnel speculated by public opinion, so as to counterattack the West in public opinion. Third, promote change by pressure. The Ukrainian garrison is exhausted under the continuous high-intensity war, and the siege may lead to internal strife. In addition, more evacuation time for civilians is also one of the considerations. Russian Defense Ministry spokesman Konashenkov said earlier that there are a large number of foreign mercenaries among Ukrainian armed personnel in Mariupol. Radio interception found that in addition to Ukrainian and Russian, Ukrainian radio dialogue also uses other languages, mainly European languages. Why is Mariupol important Mariupol is the second largest city in Donetsk region, with a population of about 400000 before the outbreak of the conflict. The largest port of the Azov Sea is located here. The capture of Mariupol means that the Russian army has built a "land bridge" along the coast of the Azov Sea to connect Crimea and Donbas, and then to the interior of Russia. The eastern coast of Ukraine will be fully controlled by Russian armed forces and the civil Azov Sea. Mariupol is the base camp of the "Asian speed battalion" of the Ukrainian National Guard. Analysts believe that the "Asian speed camp" is a nationalist militants in the eyes of Russia. Occupying Mariupol and eliminating the main force of the "Asian speed camp" means that one of the main objectives of Russia's special military action, "de Nazism" has been realized to a large extent. Shoigu reported to Putin on the 21st that during the capture of Mariupol, more than 4000 Ukrainian armed personnel were annihilated and 1478 surrendered. Yang Zhen believes that Shoigu's announcement of the progress of the Mariupol war at this time is intended to offset the negative impact of the sinking of the cruiser Moscow, the flagship of the Russian Black Sea fleet, a week ago. On the one hand, he warned the west not to act rashly, and on the other hand, he showed the Russian military and people that the dominant power in the battlefield is under control. The remaining Ukrainian troops at Yasu iron and steel plant lack heavy weapons and are unable to pose a substantial threat to the areas controlled by the Russian army and land channels. What changes will take place in the war Analysts expect that after the Russian army occupies Mariupol, it can free up its troops to carry out a new stage of special military operations. Uzbek President zelenski said on the evening of the 19th that the Russian army had launched the "battle of Donbas". Alestovic, an adviser to the Ukrainian President's office, said on the 20th that the Russian army launched a fierce attack on Kharkov, Lugansk and Donetsk on the same day. Yang Zhen pointed out that after controlling Mariupol, the Russian army is expected to alleviate the shortage of troops and then surround the main Ukrainian army in bath area. "The special military operations of the Russian army have always focused on the three objectives of demilitarization, Nazism and neutrality of Ukraine. Therefore, killing each other's effective forces as much as possible is not the primary goal." Yang Zhen said. Suslov, a professor at the European and international research center of the Russian State Higher Institute of economics, believes that the parties will still strive to sign a peace agreement in the near future. (Xinhua News Agency)