KAREN STATE, Myanmar — At first glance, Myanmar presents a rosy picture these days. After decades of isolation, the country is loosening up and opening its economy.

But some of the most lucrative opportunities come with a catch.

Many of Myanmar's prized resources are found in regions still controlled by rebellious guerrilla armies — like the gold, teak and jade in Karen State, an ethnically varied area in the country's mountainous southeast.

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The Karen have formed a rebel group, the Karen National Liberation Army (KNLA), that has successfully defended the region against the central government for more than 50 years.

Armed primarily with leftover US M-16s from the Vietnam War, the KNLA have fought for their independence in a conflict that shows no immediate signs of ceasing.