Ukrainian soldiers remember the onslaught that rained down on their positions from the middle of July 2014 onwards. Time and again they came under fire from Grad missiles and artillery shells. Now it appears that at least some of those attacks were carried out from across the Russian border.

Denys, a former fighter of the 72nd Mechanized Brigade and resident of the Kiev region, spent more than a month between July and August at a Ukrainian army stronghold near the city of Chervonopartyzansk in the Luhansk region, near the Russian border.

He says he knows for sure that out of about 500 soldiers who were together with him there, about 10 were killed. “In fact all of us had wounds of various degrees of severity,” he says. He believes total casualties in his brigade over that period amounted to hundreds of people.

“A drone showed up in the sky before every episode of shelling,” he says. “We were trying to hit it but we lacked the ammunition to be able to do that. After every shelling, we carried our wounded across the Russian border as it was impossible for us to transport them through Ukrainian territory. So in the morning we were handing over our wounded to Russians as a report on their work.”

Denys and his unit saw a massacre at Zelenopillya on 11 July, where dozens of Ukrainian soldiers were killed by Grads. “We saw a glow from that [the attack at Zelenopillya] because we were not far away from them. They burned them alive, they [the Ukrainian soldiers] didn’t even manage to jump out from trucks,” he says. “On the next day the same started to us.

“Every time when the shelling started, some guys were hiding in the armoured vehicles, some under the vehicles. But most of us were hiding in the trenches … This shelling was hugely reducing our numbers. We would easily control the border if Russians didn’t shell at us.

“Grads are not the worst thing. You can get used to them. They are more a kind of moral pressure. The most horrible was when they shelled at us from artillery, and after that we were told that the young Russian artillerists conducted their training this way … The large-calibre artillery is very scary because if this kind of shell hits close there is no way to survive. I’m 1.8 metres (5ft 9in) tall and I can stand under the ground in the shell crater that remains after it hit.”

The Ukrainians resisted the attacks but they have never dared to shoot back across the Russian border. “We didn’t even think about it, we all realised it would be the end for us.” Denys says that eventually the shelling became so intense hundreds of soldiers crossed the border into Russia.

Ruslan Pospelov, a volunteer helping soldiers of the 79th Airborne Brigade, was also near Zelenopillya in the middle of July. “We went to sleep and suddenly at about 10pm we heard whistles and a commander shouted: “To the trenches!” We ran out of tents just in underwear and jumped into the trenches. We spent half of the night there,” he recalls of his first experience under Grad fire.

Another volunteer, Serhiy Yeremenko, says the first large attack on soldiers of 79th Brigade, when one of them was killed, happened in the middle of July. Thereafter it was a constant nightmare, he says. “We were trapped under the fire ourselves, when we were delivering food for them. Some volunteers were wounded when travelling to them. After one such case the guys called us and said: ‘No need to bring us food and sacrifice other people’s lives.’”

Yeremenko says he saw proof that the soldiers were shelled from the Russian side. “We saw ourselves, near Saur Mohyla, the holes from shells fired across the Russian border. We saw it with our own eyes, we heard the sounds with our own ears.”