In the remote mountains of Myanmar's Shan state, a rebel militia near the Chinese border has since 2012 been waging a hidden war against an enemy that possesses no weapons or army.

The enemy? Opium poppies, the plant from which morphine and heroin are synthesised. This rugged area is well-known as a hotspot for the cultivation of poppies. The practise is profitable for some producers, but comes at a high social cost.

According to the United Nations Office on Drugs and Crime, the cultivation of opium in Myanmar increased by 26 percent in 2013, the biggest rise since assessments began in 2002.

Myanmar is the second-largest opium-producing country in the world after Afghanistan, and Shan State accounts for 92 percent of the country's total cultivation.

The northern part of Shan state is home to the Palaung ethnic group, many of whom have cultivated and harvested the "sleepy plant" for years. But while lucrative, the drug has been devastating the Palaung population. In some villages, more than half of the men are said to be addicts.

In response, the Tang National Liberation Army (TNLA) - an armed Palaung group - declared a war on the drug in 2012. The TNLA introduced prohibition laws in Palaung areas under their control, and today cultivating and selling drugs is strictly prohibited.

The TNLA claims to have 1,500 soldiers, who this year were ordered to destroy poppy fields during the harvest season. The commanders have accused the area's ethnic Chinese minority of cultivating poppy fields and working in collusion with local militias and Myanmar's army.

The TNLA's goal is to replace the poppy fields with other crops, like corn and tea. But the process has to be carried out gradually, because poppies are a major source of income for the peasants.