A court martial is underway at a Canadian Forces base in Manitoba for a soldier charged with sexually assaulting another soldier while they were away doing training.

In 2014, the two CFB Shilo-based soldiers were training at CFB Wainwright, Alta., with a platoon of 24 soldiers. The incident is alleged to have occurred on the final day of that training before they both returned to the Shilo base.

The accuser came forward in 2016.

The accused, now a 25-year-old corporal, pleaded not guilty to the charge of sexual assault on the first day of a military court martial Thursday, where they both testified.

The accuser, who can't be named due to a publication ban, alleged he was digitally penetrated though his clothes and had a homophobic slur said to him while he was mopping the floor one evening.

He told court that he felt a sharp, penetrating pain and was in shock as he saw the accused walking away.

The accuser, also a corporal, told court he found a two-inch-long tear in his underwear while doing laundry about two weeks after the alleged incident.

He said he suffered from the physical injuries of this alleged attack for up to a year afterwards and would often find liquid fecal matter in his underwear and wipe blood.

He didn't seek medical attention and didn't tell anyone about the alleged incident until about a year and a half later, in the summer of 2016.

"I felt it would be too awkward," said the soft-spoken soldier, who the accused and another soldier said kept to himself during the training.

Accuser asked if incident really happened

On cross-examination, the defence questioned his version of events, telling court that another soldier the accuser mentioned to police as a possible witness wasn't even in Wainwright at the time.

He was also asked if he'd ever lied before — with the defence asking point-blank if this incident actually happened and if he'd ever used his position for personal gain.

Defence lawyer Lt. Cmdr. Brent Walden asked why it took a year and half for him to report the incident.

"There's not a lot you recall, is there?" Walden asked. "You wanted to make a shocking allegation so the military police would do something about [the accused]?"

"No," he replied on cross-examination.

"That's why you told the military police that you bled from your anus for a year," Walden continued.

"No," he said again.

"You're not a homosexual?" Walden asked.

"No," he said.

'Tickle parties' common

The defence also attempted to paint a picture that showed horseplay and name-calling was common among troops who were in the training platoon and that it was just another way for soldiers to unwind and have fun — including slapping each other's butts, calling each other homophobic slurs and taking part in so-called "tickle parties" and flash mobs, where groups of soldiers would sneak up on an unsuspecting soldier in the barracks.

When the accused took the stand, he told court that he was on light duty on the day of the alleged incident after he separated his shoulder. He told court that he too was the subject of tickling, pants-pulling and even once had Rub A535 heating cream smeared on his buttocks before another soldier pushed some of the cream inside with a Q-tip.

"It wasn't meant to be malicious," he said of the behaviour, admitting that he had slapped the accuser's buttocks before. "It was done in a light spirit."

"Everybody seemed to take it quite well," said a former soldier who was on the same platoon at the time, called by the defence, in reference to the name-calling. "It wasn't derogatory or anything."

"It wasn't supposed to be crazy or anything," he said, calling it "good-natured."

The court-martial will resume Friday, when the defence is expected to call more witnesses to the stand.