Ukraine’s second largest city, Kharkiv, is believed to have been one of the invading Russian military’s first strategic targets. Home to 1.4 million people, it is located less than 20 miles from the Russian border, in northeast Ukraine. It was approached by Russian troops shortly after the invasion began last Thursday, but for three days, Ukrainian forces held the Russians at bay. Then, on Sunday, Russian troops entered the city according to the region’s governor, Oleh Synehubov. What happened next offers clues to the fierce resistance Russian soldiers are meeting in Ukraine’s towns and cities – and to why they have not yet advanced as quickly as experts initially feared they would. “The Armed Forces of Ukraine are eliminating the enemy,” Synehubov reassured the residents of Kharkiv that day. Videos uploaded to social media give a rare glimpse of the clashes on the city’s streets. One sequence of videos uploaded to social media show an attempt by a Russian unit to advance towards an important airfield and arms factory in the northeast of Kharkiv. The airfield, at the Kharkiv State Aircraft Manufacturing Company, is small – just a single runway – but might be a useful bridgehead for the Russians. CNN has geolocated and verified the authenticity of the videos. The first video, taken by a resident, shows a convoy of Russian troops surrounding military vehicles, creeping along a roadway that ends near the airfield. “There are two [military vehicles] as far as I can see,” someone says in the video. “A third one is crawling through with infantry with automatic weapons, getting ready.” Suddenly, gunfire is heard and seen. A Russian soldier kneels quickly and fires a shoulder-launched rocket towards the area where the gunfire appears to be coming from. A second video, taken after the firefight, shows the military vehicles reversing in an apparent retreat. The Russian troops are seen huddled behind their vehicles. A Reuters journalist who went to the location after the firefight shot video showing one of the Russian vehicles from the military convoy abandoned and a significant amount of blood staining the snow on the ground nearby. The Reuters journalist spoke with a resident, identified as Yevgeniy, who told them that at least one Russian soldier had been killed there. “After we’ve killed this one the others run away,” Yevgeniy told Reuters, pointing to a patch of blood in the snow. He tells the journalist there were between 12 and 15 people in the group. “They won’t take Kharkiv,” he insists. “They have run back to where they came from. They don’t have good navigation you see. Nothing works for them. They came and were hiding behind the houses.” The troops’ efforts to retreat appear to have been stopped by another attack. A convoy of vehicles – of the same type as those seen in the previous clips – is seen on fire in another video. “This is how we greet the b*tch Russian army,” someone is heard shouting in the video. “Come here and blindfold him. And this will happen to anyone who comes to us here on Kharkiv soil.” It’s not possible to say definitively that the Russian trucks seen on fire are the same as those filmed trying to reach the airport, but they are in the same location, are the same type, and bear the same markings. Another video apparently taken later at the site of the abandoned military convoy – the vehicles are no longer on fire – shows Ukrainian troops engaging. Amid the firefight, a Ukrainian soldier steps out from the wall and is seen firing a shoulder-launched rocket. Watching the video, retired Gen. Mark Hertling, national security and military analyst for CNN, said the Ukrainian unit was equipped with rocket-propelled grenades. “You see that force, that small squad there of about 10 guys, the guy up furthest away from us is repeatedly firing rocket-propelled grenades, he’s fired by my count about five of them, he is handing off the launcher to another guy, they are reloading and he is ready to shoot again,” he said. “And everybody else, you look at the cool, calm, collected approach by these soldiers under fire, they’re not afraid, they’re ready to kick some butt,” he added. Later, another video shows Ukrainian troops around the convoy, appearing to rummage through the abandoned vehicles. Sporadic gunfire is heard and some Ukrainian forces move along a wall in the background. “Slava Ukraini,” says someone in the video (“glory to Ukraine”). Swift response But on Monday, Russian troops returned to the northeastern suburbs of Kharkiv and renewed their attack on the city. Multiple social media videos geolocated by CNN show rockets exploding closely together in a residential area of the Saltivka neighborhood, close to a supermarket. One showed a rocket booster lodged in the street pavement, as civilians looked on. “It’s more hellish in Kharkiv today than it was yesterday,” said Ukraine’s Prosecutor General Iryna Venediktova, posting on Facebook. According to Kharkiv City Council, the latest shelling left one female civilian dead, and 31 people – 15 servicemen and 16 civilians – wounded. In recent days, the city council has recorded seven fatalities – two servicemen and five civilians – and 44 wounded, including 20 servicemen. “Kharkiv has just been subjected to massive Grad shelling! Dozens of victims,” Anton Gerashchenko, an advisor to Ukraine’s Ministry of Internal Affairs, said Monday describing the situation there as “a nightmare.” Russia maintains that it does not target civilians.