Three reservists died and others were affected by heat illness during the march in high temperatures in July 2013, the court martial heard.
There were a number of routes for those taking part in the Brecon Beacons exercise, with candidates starting at different times.
Lance Corporal Edward Maher was on the black route and went through the penultimate check point at 1.22pm.
The fact he was in difficulty was only realised by defendants 1A and 1B at 4.10pm, the board at the Court Martial Centre in Bulford were told.
L/Cpl Craig Roberts went through the penultimate check point and was identified as having difficulties at 3.36pm.
Corporal James Dunsby, who died in hospital after collapsing on the march, was on the red route and noted to be in difficulty at 4.10pm.
Two other soldiers, referred to as C1X and C1W, suffered non-fatal heat illness.
Prosecuting, Louis Mably QC told the court martial that the first heat illness related casualty was at about 11am.
“He came into check point one and spent time under medical assessment and obviously was in poor shape,” Mr Mably said.
The casualty was suffering from vomiting and diarrhoea, signs of heat illness, and voluntarily withdrew from the march.
At 12.14pm, a candidate reached check point four on the red route and was medically withdrawn after being diagnosed with heat illness.
Another candidate, C1W, reached that check point at 12.22pm and was noted to be unsteady on his feet.
C1B allegedly agreed for C1W to continue after being told he was fit to do so but would not continue the course in the allowed time.
“This candidate, 1W, never made the next check point,” Mr Mably said.
“He became lost on the hill and became a heat illness casualty and hours after he had left the check point, it was realised there was an issue with him – that he wasn’t moving.”
1W was identified as being in difficulty at 3.46pm and was withdrawn from the march.
Another collapsed between two check points, with a passing candidate activating his “man down” alarm, worn by all on the march, at 12.46pm.
He was assessed and diagnosed with heat illness.
“By the time his man down alarm went off and he had been diagnosed, it was clear that there was a heat illness issue with this exercise,” Mr Mably said.
“Candidates were struggling.”
L/Cpl Roberts passed a drill at the penultimate check point but was later found unconscious about 1.5km from the finish by another candidate, C1D.
His “man down” alarm was activated at 3.36pm, with emergency services arriving about an hour later.
L/Cpl Roberts was pronounced dead at 5.10pm, with his cause of death later found to be hypothermia.
The court heard L/Cpl Maher was identified as a “slow-moving candidate” at 4.10pm, having reached the penultimate check point at 1.22pm.
Mr Mably said L/Cpl Maher’s tracker revealed he had not moved “very far at all” between leaving the check point and being found.
“It was two hours and 38 minutes since he had left the check point at 1.22pm,” he said.
L/Cpl Maher was discovered at 4.55pm.
“He was sitting upright with his Bergen on, with a half full bottle of water in one hand and a half eaten chocolate bar in the other,” Mr Mably said.
“He appeared to be dead.
“A post-mortem examination revealed that his death was caused as a result of the effects of hyperthermia.”
At 4.10pm, Cpl Dunsby was noticed to be static, having left his penultimate check point at 2.51pm.
He was found unconscious at 4.52pm and an ambulance arrived at the scene at 5.18pm.
Cpl Dunsby died in hospital on July 30.
The court martial was told that at 4.55pm, a civilian walker activated the “man down” alarm of another candidate, 1X.
At 5.40pm, the candidate was treated at the scene for heat illness and taken to hospital. He survived.
“It is clear that something went terribly wrong,” Mr Mably said.
“The defendants lost control of events and ended up in a position where they couldn’t account for a number of candidates.”