The scale of the devastation suffered by Ukrainian forces in southeastern Ukraine over the last week has to be seen to be believed. It amounts to a catastrophic defeat and will long be remembered by embittered Ukrainians as among the darkest days of their history.

A week ago a major rebel offensive began. On September 3 on a sixteen-mile stretch of road from the village of Novokaterinivka to the town of Ilovaysk, I counted the remains of sixty-eight military vehicles, tanks, armored personnel carriers, pick-ups, buses, and trucks in which a large but as yet unknown number of Ukrainian soldiers died as they tried to flee the area between August 28 and September 1. They had been ambushed by rebel forces and, according to survivors, soldiers from the army of the Russian Federation.

These destroyed vehicles were of course only the ones I could see—those that were not destroyed are now in the hands of rebels. In Novokaterinivka, which is twenty-eight miles southeast of the rebel-held city of Donetsk, the body of a Ukrainian soldier was folded over the high power cable onto which he had been flung when his armored vehicle exploded, his clothes hanging off him. In what was left of the vehicle nearby were the charred remains of half a man and the grilled body of another, left where he had been sitting when he was killed.

On September 3, eighty-seven bodies were reported to have arrived in Zaporizhia, a large city in the region that is under Ukrainian control. But, more are yet to be found. Quite apart from the appalling military setback is the humiliation. At one ambush site two fresh graves marked with crosses made of sticks indicated that the dead had been buried close to their burned out vehicles by the side of the road. On the main street of Novokaterinivka locals posed for pictures in front of destroyed vehicles and cars that had been jacked up with logs because undamaged wheels had been unscrewed and looted. Euphoric rebel soldiers there told us they were “cleaning up”—looking for remaining Ukrainians who had fled into the fields and were still there.

A colleague told me that nearby, two Ukrainian soldiers had jumped out onto the road and stopped his car. They were about eighteen years old, he said, had been hiding in a field of sunflowers, and looked as though they had not slept for days. When they saw a car with the initials TV taped onto it, which is used to signify that there are journalists in it, they took their chance. They begged him and his colleagues for a lift and then for food and water. The Ukrainian media has begun to report on stories of stragglers limping in to safe territory and more than five hundred Ukrainians are reported to have been captured in this area. One called Sergey, who had been detained and released, said that the men who captured him said they were Russian regular soldiers: “They told us they had arrived two weeks earlier. They were very young.”

The fortunes of war have changed dramatically in the past two weeks. In spring, anti-Kiev rebels, taking the new and revolutionary Ukrainian government by surprise, seized towns and cities across the two predominantly industrial and mining regions of Donetsk and Luhansk. At first, Ukrainian forces either fell apart, were captured, or defected to the rebel side. By summer, however, the Ukrainians were better organized and went on the offensive driving the rebels back.

Rebel-held Luhansk came under a virtual siege, and was heavily shelled by Ukrainian forces, though bizarrely it is still possible to get to the town on a suburban train. Large parts of Donetsk too came under shelling from Ukrainian forces. Some areas have been badly damaged and targeting has been so woefully inaccurate that hundreds of civilians have been killed in the process. The result is that, by August, many ordinary people who did not care that much about who ruled them hated the government in Kiev and Ukraine as a whole.

Then, in the last two weeks of August, everything changed again. The Ukrainians said that regular Russian troops were crossing the border, a contention supported by western intelligence reports. More and more stories are being written in the Russian press too about soldiers killed in action in Ukraine, though the Russian government flatly denies that any regular soldiers—as opposed to volunteers who have come on their own—have crossed the frontier. However not only is there mounting evidence of the presence of regular Russian soldiers but the fact that the military situation has changed so rapidly also suggests the rebels have acquired new strength. Today, Donetsk is a much safer city than it was a few weeks ago. The reason for that is that Ukrainian forces have been pushed back though the two sides still trade artillery and Grad rocket fire every day.

This dramatic shift in the conflict is also made clear in the carnage on the road between Ilovaysk and Novokaterinivka and in the middle of fields across which some vehicles had tried to escape. Many of the vehicles, which had been coming in different convoys, from different places—though the bulk of them from Ilovaysk—had been not only professionally ambushed but utterly destroyed, meaning that much bigger weapons than rocket-propelled grenades had been used. Tank turrets had been hurled far from the rest of the tanks to which they had been attached, for example.

What all this reveals is that those attacking the pro-government forces were highly professional and using very powerful weapons. It also suggests there must have been a lot of men along the roads to be able to take out so many vehicles and soldiers, more or less at the same time. Gennadiy Dubovoy, who said he was chief editor of a rebel newspaper and who was dressed in military fatigues, estimated that there had been 2,000 Ukrainians in flight when the ambushes occurred.

The fighting in Ilovaysk began on August 7 when units from three Ukrainian volunteer militias and the police attempted to take it back from rebel control. It was heavily shelled. The rebels were never driven out, though, but held on to part of the town. Then, on August 28, they were able to launch a major offensive, with help from elsewhere, including Donetsk—though “not Russia,” according to Commander Givi, the thirty-four-year-old head of rebel forces here. By September 1 it was all over and the Ukrainians had been decisively defeated.

The Ukrainians claim that their units had made a deal to gain free passage out of Ilovaysk and that Russian President Vladimir Putin himself had said they should be allowed to go. But Commander Givi, whose real name is Mikhail Tolstykh and who said that he worked in a rope factory before the war, denied there had been any agreement. The ambushed forces, he said, were militias not regular soldiers—“we don’t know who they are.” Their numbers had been boosted, he claimed, by foreigners, including Czechs, Hungarians, and “niggers.” When he arrived at his HQ he came in a big, shiny car with music blasting and some of his men in the back cradling guns in their laps with the muzzles sticking out of the windows.

The next targets, says Commander Givi, are the port of Mariupol in the south, on the Azov Sea, and Sloviansk, which had been a rebel bastion until the rebels retreated from it on July 5.

The situation on the Sea of Azov, an appendage of the Black Sea surrounded by Crimea in the west, southeastern Ukraine in the north, and Russia in the east, has, as in the regions further north, changed dramatically in the last couple of weeks. On August 27 the border crossing to Russia was taken by the rebels after it had been shelled with a few mortars and the Ukrainians there, with far less firepower, fled. They fled the nearby town of Novoazovsk too. On August 30 I saw a group of twenty people with their arms stretched up to heaven by the main checkpoint on the eastern outskirts of Mariupol praying for peace and for the protection of the city while volunteers assembled to dig trenches.

That weekend it was unclear how far the rebels had advanced because no one seemed to be in control of large areas. We passed a checkpoint close to Novoazovsk manned by men who seemed to be locals but were eating ration packs clearly marked as Russian army-issue. Behind us at various points we had seen tanks dug in. The road from the border with Russia appeared to be rutted with tank tracks, though Aleksandr Demonov, the rebel press spokesman, claimed that the marks had been made by a bulldozer pushing giant concrete bollards that the Ukrainians had put on the road out of the way.

At the village of Bezimenne, where you can see the sea from the road, we stopped to ask some people who was manning the next checkpoint and if it was safe. There was a Russian checkpoint at the exit of the village, they said. They could have used “Russian” to mean “rebel,” but in this case the men, who had modern communications equipment and some jeeps of a type which I have not seen elsewhere, did not seem in the mood to chat and ordered us to go. On the other side of the road was a tank, whose cannon was not pointing ahead to the Ukrainians whom we met a few minutes further down the road but out to sea.

As we sped away from the “Russians” we could see a column of black smoke rising from the sea. When we got to the Ukrainian checkpoint the men told us that it was a coastguard cutter that had been hit, they thought by a tank. They were from the Azov Battalion, one of the Ukrainian volunteer militias. On their vehicles and their arm flashes they had the “wolfsangel,” a neo-Nazi symbol, which is their insignia and which tells you much of what you need to know about their background. (On September 4, they were driven out of this position as the rebels, and presumably regular Russian forces, too, advanced.)

In Mariupol, people were packing the 5:05 PM train to Kiev. It was the end of the summer holidays, but many were also leaving because of the situation. Many of those leaving Mariupol were already refugees from Donetsk and elsewhere. Mariupol felt eerily empty, and like Donetsk from which perhaps half of its million people have fled, many of those who remain are elderly. The city is sharply divided. Half those I talked to supported the government in Kiev and the other half the rebels. But people are confused and loyalties shifting. Some told me they used to support the rebels but now supported Ukraine and vice versa.

Back in Ilovaysk, I went to see the school in which the Ukrainian militias had been living before being driven out. Extraordinary footage has been filmed of their days here showing them shooting from the windows and dousing fires started by incoming bullets. Now it is totally silent.

There were eleven destroyed vehicles around the school. In a store cupboard by the gym where many had been sleeping I came across a polystyrene Father Christmas. Outside there were some graves in which—according to Vergil, the twenty-year-old soldier who had been detailed by Commander Givi to show us around—the battalions had buried civilians they had killed. There was no way to verify this and the graves might well contain their own dead, though Vergil said that they had taken those bodies away. Vergil told us that he was from Luhansk and had been doing his Ukrainian military service in April. His unit had been captured and told that they could either leave or join the rebels.

On the road back to Donetsk there is a long straight stretch lined by tall trees. In the distance we could see something. Realizing it was a military convoy, we pulled over and I jumped out. The car leading the convoy of four tanks and three APCs topped with dozens of men screeched to a halt, as did all the cars that were behind us. Armed men jumped out of the car demanding to know what we were doing—one jabbing his fingers at the TV tape on the car. A fat, angry man with gold front teeth demanded our phones. A stocky lady in her fifties sat in the back of their car pointing her sniper rifle out of the window at my colleague a few meters away.

After a few minutes the neat tall man standing in front of me told me to put my hands down and asked me in good English where I was from. He told me he had once lived in Lausanne. As the situation cooled the angry fat man returned our accreditations and passports and the woman still pointing her gun at my female colleague began blowing kisses at her. The fat man got back in his car with our phones but our translator stuck her foot in the door yelling at him to return them, which eventually he did. The entire convoy then juddered back into action.

The tanks looked relatively modern. As they pulled away, a man whose head was sticking out of the hatch at the top of a tank waved at us. His features were central Asian. A large proportion of Russian conscripts are central Asians. The men on top of the APCs looked like locals, but if the tanks were Russian army ones, this could explain the otherwise inexplicable rage of the fat man encountering journalists seeing his convoy.

The war has a taken a decisive turn. There is now talk of a ceasefire, an advance on Mariupol, new sanctions on Russia, and what NATO might do at its summit in Wales now under way. According to the UN a million people have already been displaced by the war. Putin reportedly told José Manuel Barroso, the president of the European Commission, that he could take in Kiev in two weeks. The Ukrainians have suffered major reverses in the past few days, but they have not lost the war yet, though Ukrainian President Petro Poroshenko must now be wondering if he should cut his country’s losses and sue for peace. Poroshenko knows that alone, Ukraine cannot win a war against Russia; and one hundred years after the beginning of World War I, it is not clear that anyone is going to rush to help him win either.