KHERSON, DECEMBER 26

Their first battle plan was outdated the moment the dam crumbled. So the Ukrainian special forces officers spent six months adapting their fight to secure a crossing to the other side of the Dnipro River in southern Ukraine.

But it wasn't enough just to cross the river. They needed backup to hold it. And for that, they needed proof that it could be done. For one of the officers, nicknamed Skif, that meant a flag - and a photo op.

Skif, Ukrainian shorthand for the nomadic Scythian people who founded an empire on what is now Crimea, moves like the camouflaged amphibian that he is: Calculating, deliberate, until the time to strike.

He is an officer in Center 73, one of Ukraine's most elite units of special forces - frontline scouts, drone operators, underwater saboteurs. Their strike teams are part of the Special Operations Forces that run the partisans in occupied territories, sneak into Russian barracks to plant bombs and prepare the ground for reclaiming territory seized by Russia.

Their mission on the more dynamic of the two main fronts in the six-month counteroffensive reflects many of the problems of Ukraine's broader effort. It's been one of the few counteroffensive successes for the Ukrainian army.

By late May, the Center 73 men were in place along the river's edge, some of them almost within view of the Kakhovka Dam. They were within range of the Russian forces who had controlled the dam and land across the Dnipro since the first days after the February 2022 full-scale invasion. And both sides knew Ukraine's looming counteroffensive had its sights on control of the river as the key to reclaim the occupied south.

In the operation's opening days, on June 6, an explosion destroyed the dam, sending a wall of reservoir water downstream, killing untold numbers of civilians, and washing out the Ukrainian army positions.

'We were ready to cross. And then the dam blew up,' Skif said. The water rose 20 meters (yards), submerging supply lines, the Russian positions and everything else in its path for hundreds of kilometers. The race was on: Whose forces could seize the islands when the waters receded, and with them full control of the Dnipro?

For most Ukrainians who see them on the streets in the nearly deserted frontline villages of the Kherson region, they are the guys in T-shirts and flip-flops - just regular people. The locals who refused to evacuate have all become accustomed to the sounds of war, so even their unnerving calm in the face of air raid alarms, nearby gunfire and artillery doesn't seem unusual.

AP joined one of the clandestine units several times over six months along the Dnipro. The frogmen are nocturnal. They transform themselves from nondescript civilians into elite fighters, some in wetsuits and some in boats. In the morning, when their operations end, they're back to anonymity.

They rarely take credit for their work and Ukrainians rarely learn about their operations. But Russian military statements gleefully and erroneously announcing the destruction of Center 73 are an indication of their effectiveness.

JUNE 2023

The men had the most modern equipment, night-vision goggles, waterproof rifles that can be assembled in a matter of seconds, underwater breathing apparatus that produces no surface bubbles, and cloaks that hide their heat signature during nighttime raids.

It was a matter of days before the start of the counteroffensive, and Center 73 had already located the Russian positions they would seize on the Dnipro River islands. Skif's men were within earshot of the June 6 explosion that destroyed the Kakhovka Dam, flooded vast stretches of the Kherson region, and upended Skif's attack plan.

An AP investigation found Russian forces had the means, motive and opportunity to blow up the dam.

Both the Russians and Ukrainians retreated from the river to regroup - Russians to the south and Ukrainians to the north.

Abandoned homes, clubs, shops became headquarters, with banks of computer screens filling the rooms and improvised weapons workshops nearby. Always secretive, frequently changing locations, they meticulously plan every operation, they sleep only a few hours during the day with curtains closed.

They wake around sunset, load gear into a 4X4 and drive to a different point on the riverbank to scout new routes for a counteroffensive, provoke Russian forces into shooting at them to pinpoint the enemy's location, retrieve soggy caches of supplies with their boat. Periodically, they captured a Russian soldier stuck in a tree or found a clutch of landmines washed up on shore.

And they themselves were stuck. Other special forces took part in battles in eastern Ukraine, the other main front in the counteroffensive. Skif's men waited patiently for the water to subside so they could seize positions and lay the groundwork for the arrival of infantry and marines in the Kherson region.

Skif, a veteran of the 2022 battle for Mariupol who had survived 266 days as a prisoner of war, wanted to fight. He had been part of Center 73 before Mariupol and rejoined after he was freed in a POW exchange.

Ukraine created its special forces in response to Russia's lightning-fast annexation of Crimea and invasion of Donbas in 2014, a precursor to the wide-scale invasion of Ukraine in 2022.

'We realized that we were much smaller in terms of number than our enemy,' said Oleksandr Kindratenko, a press officer for Special Operations Forces. 'The emphasis was placed on quality. These were supposed to be small groups performing operational or strategic tasks.'

He said they were trained and equipped in part by Europeans, including those from NATO countries, but their own recent battle experience means they are now as much teachers as students.

Tasks that the unit considers routine - scouting as close to Russians as possible, planting explosives under their noses, underwater operations - most soldiers would consider high-risk. High-risk missions are practically a death wish.

Skif knew he first had to plan and persuade the generals that if his men could secure a bridgehead - a strategic crossing point - it would be worthwhile to send troops. And that would mean high-risk river missions.

'My phone book is a little graveyard,' he said. 'A lot of good, decent people are dead. They were killed on the battlefield. One burned to death in an armored truck. One was shot by howitzers. Somebody stepped on a landmine. Everyone died differently, and there are so many of them.'

JULY – AUGUST 2023

The water retreated in July. The Russians and Ukrainians advanced again toward the river from opposite directions, the Russians from the south and Ukrainians from the north.

Groups of Center 73 scouted and advanced along the river. The mission for Skif's unit was to reclaim an island near the dam, now a web of cracked mud and dead trees. Their network of spies in the Kherson region, as well as drones and satellite images, told them where Russian forces had re-positioned.

They disembarked the boats and moved in, walking through the bare branches of the forest through swarms of mosquitoes so loud their bodycam picked up the sound. One of the men tripped a wire connected to a grenade and flung himself as far as he could away from the Russian explosive.

Just as the shrapnel pierced his back, mayhem broke out. The injured Ukrainian crawled toward the unit's waiting boat 3 kilometers (2 miles) away, as the Russian troops who set the boobytrap rained gunfire on them. Skif's men made it to the boat, which sprang a leak, and retreated back to their side of the Dnipro. Russians established their position on the island, and it took weeks more for the Ukrainians to expel them.

Then new orders came. Go upstream and breach Russian defenses beneath a destroyed railway bridge.

The men had an often-underestimated advantage over their Russian enemy: Many Ukrainians grow up bilingual and understand Russian communications intercepted in real time, while Russian soldiers need a translator for Ukrainian.

So when Skif's unit started picking up Russian radio communications by the railway bridge, they immediately grasped how many men they were up against and the kind of munitions they would face. They made the crossing, avoided the Russians, and waited for backup,

That's when their advantage evaporated. In a single battle, the Russians sent Iskander missiles and dozens of drones, dropping hundreds of grenades.

'In the air, they had absolute dominance compared to us and they held the ground,' he said.

The backup was nowhere near enough. Ukrainian forces retreated under heavy fire. More men out of commission and another difficult task ahead.

SEPTEMBER - OCTOBER 2023

A lucky thing happened soon after that battle. A Russian officer who claimed he'd been opposed to the war since its beginning was sent to the front in Kherson. It was, he later said, every bit as bad as he'd feared.

He made contact with Ukrainian intelligence and said he had 11 comrades who felt similarly. The group surrendered to Skif and his men.

The Russians told Skif exactly what he needed to know about their unit on the island they were now tasked with taking, just outside the village of Krynky.

He was sure he could take the island and more with 20 experienced men. But not without the promise of sufficient backup so Ukrainian regular forces could hold the territory. Fine, his commander said. He'd get the backup - if he returned with footage of his unit in the village hoisting the Ukrainian flag.

And that's how, in mid-October, a Ukrainian drone carrying the national blue and yellow flag came to fly above Krynky at just the moment Skif and his men made their way to the occupied village across the river. They got their photo op to prove the road was cleared, sent it to the military headquarters, and established the bridgehead.

NOVEMBER - DECEMBER 2023

Multiple Ukrainian brigades were sent to hold the position and have been there ever since.

But nighttime temperatures are dipping well below freezing, and Ukrainian forces are vastly underequipped compared to the Russians nearby. Holding and advancing in winter is much harder on soldiers' bodies and their morale.

In recent weeks, Russia has sent waves of glide bombs - essentially enormous munitions retrofitted with gliding apparatus to allow them to be launched from dozens of kilometers (miles) away, as well as swarms of grenade-launching drones and Chinese all-terrain vehicles, according to the Institute for the Study of War and the Hudson Institute, two American think-tanks analyzing open-source footage from the area.

In a news conference earlier this month, Russian President Vladimir Putin addressed the battle and acknowledged Russian forces had pulled back 'several meters.' But he insisted Ukrainian forces were battling pointlessly and losing far more than they gained.

'I don't even know why they're doing this,' Putin said.

Despite having never fully controlled the territory during the six-month counteroffensive, Russia claims it as its own.

And Ukrainian forces and Center 73 keep fighting into the new year.

'This is our work,' Skif said. 'No one knows about it, no one talks about it, and we do it with little reward except to benefit our country.'