Ukraine’s army and civilian volunteers last spring stymied President Putin’s plan to decapitate Ukraine’s government in three days. The invaders were not only stopped at Kyiv’s northern suburbs, but expelled back to Belarus.

Turning on Kharkiv, Russian forces relentlessly shelled Ukraine’s second largest city, damaging or destroying a quarter of the housing in a city of 1.4 million. Ukrainians dug in their heels. By October, the invaders were expelled from Kharkiv Region.

Last month, President Putin took to a stage in Red Square in Moscow and declared that  Kherson and three other regions in Ukraine would be part of  Russia ‘forever.’

But on Friday, Russia’s Defense Ministry announced that its military retreat from Kherson City “has been completed.” On Wednesday, Russian officials had ordered the retreat, saying further defense of Kherson, the only Ukrainian regional capital captured during the 9-month war, would be “futile.” This forces the Kremlin to give up plans to take the key Black Sea ports of Odesa and Mykolaiv.

A former Kremlin advisor, Sergei Markov, calls the decision to leave Kherson “Russia’s biggest geopolitical defeat since the collapse of the USSR.” War Gonzo, a pro-war Telegram account, told its 1.3 million mostly Russian subscribers that the announced withdrawal is “a black page in the history of the Russian army. Of the Russian state.”

Ukrainian officials say that some Russian soldiers in Kherson City have changed into civilian clothes.  River crossings were reportedly chaotic with heavy Ukrainian shelling Thursday night. Following a strategy adopted by the Red Army in World War II, retreating Russian soldiers have mined apartments and sewers.

On Thursday, Ukrainian soldiers liberated 41 rural settlements, with patrols coming within miles of Kherson City. After nine months of Russian occupation, Ukrainian collaborators are losing confidence in their future. The collaborationist administration has relocated to Skadovsk, a lowkey port city with a pre-war population of 17,000.

When I vacationed there with my family two years ago, I found a peeling Black Sea resort town with a port that received only one ship that year. The Kyiv government was trying to sell the port to a Turkish buyer.

For fleeing pro-Russian administrators, Skadovsk has a big advantage. It is the closest port to Russia-controlled Crimea, about an hour by motor boat across a normally placid gulf.

One administrator, Kirill Stremousov, won’t make it. On Wednesday morning, Mr. Stremousov, deputy head of the Russian-installed regional administration, announced on his Telegram channel that the Russian military was in “full control” of Kherson. Hours later, Russian officials announced that Mr. Stremousov was killed in a car crash. Mr. Putin quickly granted him the Order of Courage.

There is more to Kherson Region than Kherson City. Ukraine now faces a tough fight to regain control of the full Kherson region. Since the 1960s, the eastern part of the region has supplied Dnipro River water to Crimea, the semi-arid peninsula jutting out into the Black Sea. 

Constructed from 1957 to 1963, the 250-mile long canal was hailed at the time as one of the “Great Construction Projects of Communism.” In 2014, at the time of Russia’s takeover of Crimea, the canal was supplying as much as 85 percent of Crimea’s water.

Since then, Mr. Putin stationed tens of thousands of troops on the peninsula, but did not invest in desalinization plants to obtain drinking water from the Black Sea.

Equally important to the Kremlin, the Kherson region is a key part of a “land bridge” to Crimea from Russia. A 250-mile east-west road connects two Ukrainian regions controlled by Russia since 2014, Donetsk and Crimea.

To circumvent Ukrainian control of this land route, Mr. Putin ordered the construction of a 10-mile, $3.7 billion road and rail bridge connecting Russia’s mainland with Crimea. Passing over the Kerch Strait, the bridge was personally inaugurated by Mr. Putin on May 15, 2018. 

On October 8, the day after Mr. Putin’s 70th birthday, a bomb severely damaged the bridge, dropping two spans of one lane into the water. On Tuesday, the bridge was closed to all road traffic as work started on what is expected to be a year-long repair project. Rail traffic continues. Trucks and cars are crossing the strait by ferry.

More threats to Putin’s land bridge will come as Ukraine reoccupies the west bank section of Kherson Region. This puts Ukraine’s highly accurate, Western-supplied artillery within range of three Russia-controlled roads that supply Crimea.

Looking ahead, Ukraine’s leaders now set their sights on a fourth ‘K’ defeat for Russia’s Army: Krim, or Crimea.