As the war in Ukraine entered its fourth week on Thursday, British intelligence said the advance of Russian forces had mostly bogged down on all fronts amid what it described as “staunch and well-coordinated” Ukrainian resistance. “Russian forces have made minimal progress on land, sea, or air in recent days and they continue to suffer heavy losses,” British intelligence said in a March 17 update. Heavily outnumbered Ukrainian forces have prevented Russian troops from capturing any of Ukraine’s biggest cities so far despite the largest assault on a European state since World War Two. “The vast majority of Ukrainian territory, including all major cities, remains in Ukrainian hands,” British intelligence said. More than 3 million Ukrainians have fled the country and thousands of civilians and military service members have lost their lives amid the fighting. Mariupol has suffered the worst humanitarian catastrophe of the war, with hundreds of thousands of …