As the monsoon rains continued to pour one night in August last year, Wunna Kyaw and a few other soldiers walked away from their military base in Myanmar.

Only hours before their scheduled deployment, the military was fighting to contain armed pro-democracy groups' attacks in an area engulfed in intense fighting, according to a report published today on The Guardian.

"I believed I would die if I did not defect," the UK newspaper quotes Wunna Kyaw as saying.

They slipped away from their compound in Kayin, or Karen state, while the commander and senior officers slept -- an action that could have resulted in the death penalty or at least seven years in prison.

Apart from fear, his decision was driven by is objection to military violence against civilians. "I didn't want to stay there anymore.

"I feel sorry for the people – people of my parents' age are being killed, and their houses destroyed for no reason. I saw it, I witnessed that," he says.

Over the months that followed, thousands more military personnel – including entire battalions – are reported to have surrendered. Some soldiers claim that their political or moral objections caused them to defect. In many others, they surrendered after being overwhelmed by their opponents, according to The Guardian report.

Since seizing power in a coup in February 2021, Myanmar's military has struggled to subdue opposition to its rule, including from pro-democracy groups and armed groups of ethnic minorities.

Pressure on the military increased dramatically on October 27, when an offensive named Operation 1027 was launched in northern Shan state by a coalition of armed ethnic-minority groups, the Three Brotherhood Alliance, in coordination with newer anti-coup fighters.

The military, already stretched and fighting on multiple fronts, was apparently taken by surprise. The offensive made rapid advances along the border with China and prompted offensives in other regions, according to the report.

Progress by resistance groups elsewhere has been mixed, and analysts' caution that initial hopes that the military was on the brink of a wider defeat were premature.

But, The Guardian report said, the losses that have occurred since October in the north alone -- aircraft shot down, weapons seized, key towns and supply routes lost -- has proved a humiliation for the military, and stirred internal anger towards its leadership.

"When I served in the military it would be very, very rare news if a captain is killed -- not even captured," says Htet Myat, an activist who served as a captain in the military before he defected on political grounds in 2021.

"It never happened that military fighter jets were taken down or tanks seized by the enemy side or missiles taken by the enemy side," he adds.

By early January, anti-junta fighters captured the key town of Laukkai near the Chinese border. Ye Myo Hein, an analyst at the Wilson Center, a Washington-based thinktank, described it as "the largest surrender in the history of Myanmar's military", saying he understood that 2,389 military personnel, including six brigadier generals, had surrendered.

Some of the six generals had reportedly been sentenced to either death or life imprisonment by the junta for surrendering. The junta has since denied this, according to the report.

Since Operation 1027, more than 4,000 soldiers are estimated to have defected or surrendered, according to Dr Sasa, minister of international cooperation for Myanmar's national unity government, which was formed to oppose the junta.

According to The Guardian, Sasa said this was in addition to 14,000 military personnel who defected since the 2021 coup through programmes set up by activists to persuade soldiers to join the resistance.

However, Ye Myo Hein estimates there have been at least 10,000 defectors, including soldiers and police. "Additionally, there has been a higher rate of deserters, historically a prevalent issue in the Myanmar military," he said, adding that there was a growing trend of mass surrender, especially since Operation 1027.

"The surrender of entire battalions -- and, more recently, entire regional operation commands -- is unprecedented in the Myanmar military's history," he said.

The Guardian quotes Morgan Michaels, a research fellow for south-east Asian politics at the International Institute for Strategic Studies, as saying, "The bigger picture is whether or not the morale issue and the embarrassment issue could generate some sort of instability inside the regime."