The military now controls less than at any time since they first took control of the country in 1962, according to the US-based Armed Conflict Location and Event Data Project (Acled).
Co-ordinated operations between ethnic armies and civilian militia groups have put the military on the back foot.
After heavy territorial losses earlier this year Commander-in-Chief Min Aung Hlaing made a rare admission that his forces were under pressure.
The leaked Watermelon intelligence from within the military is helping to tip the balance. Two years ago, the resistance set up a specialised unit to manage the growing network of spies and to recruit more.
Agents like Win Aung [not his real name] collect the Watermelon leaks, verify them where possible, and then pass them on to the rebel leaders in the relevant area.
He is a former intelligence officer who defected to the resistance after the coup. He says they are now getting new Watermelons every week and social media is a key recruitment tool.
Their spies, he says, range from low-ranking soldiers to high-ranking officers. They also claim to have Watermelons in the military government - "from the ministries down to village heads".
They are put through a strict verification process to ensure they are not double agents.
Motivations for becoming a spy vary. While in Kyaw's case it was anger, for a man we are calling "Moe" - a corporal in the navy - it was simply a desire to survive for his young family.
His wife, pregnant at the time, pushed him to do so, convinced the military was losing and he would die in battle.
He began leaking information to the Watermelon unit about weapons and troop movements.
This kind of intelligence is crucial, says pro-democracy rebel leader Daeva.
The ultimate goal of his resistance unit is to take control of Yangon, Myanmar's biggest city and his former home. But they are a long way off.
The military retains the majority of major urban areas - home to crucial infrastructure and revenue.
"It's easier said than done to attack and occupy [Yangon], Daeva says. "The enemy will not give up on [it] easily."
Unable to physically penetrate the city, Daeva from his jungle base directs targeted attacks by underground cells in Yangon using Watermelon intelligence.
In August, we witnessed him making one such call. We were not given the details but were told it was to direct an assassination attempt on a colonel.
"We will do it inside the enemy's security parameters," he told them. "Be careful, the enemy is losing in every direction," he added, telling them that this meant they were more likely to be on alert for infiltrators and spies.
Daeva says several major attacks by his unit have been the result of tip-offs.
"We started with nothing and now look at our success," says Daeva.
But it comes at a cost. Watermelons have to live in fear of both sides, as navy corporal-turned spy Moe discovered.
Deployed from Yangon to Rakhine - a border region where the military is fighting an ethnic group siding with the resistance - he had to live with the terror that his intelligence could mean he himself was attacked.
In March this year, his anchored ship was hit with a projectile missile, followed by open fire. "There was no place to run. We were like rats in a cage." Seven of his fellow soldiers were killed in the rebel attack.
"Our ability to protect [the moles] is very limited," admits Win Aung. "We can't publicly announce that they are Watermelons. And we can't stop our forces from attacking any particular military convoy."
He says that when this is explained to the Watermelons, however, they do not falter. Some have even responded: "When it comes to that moment, don't hesitate, shoot."
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Additional reporting by Becky Dale, Muskeen Liddar, Hla Hla Win, Phil Leake, Callum Thomson, Pilar Tomas, Charlotte Attwood and Kelvin Brown. Methodology support by Prof Lee Jones, Queen Mary University of London.