New Delhi, Aug. 18 -- En Poy was minding cattle in a former Khmer Rouge stronghold in Cambodia when he set off his first land mine.

The blast from the rusty relic he picked up cost him an arm and an eye. It also inspired his career with the nonprofit Cambodian Self Help Demining, which clears land mines and unexploded ordnance across the country, deadly remnants of wars from the last century.

Groups like Poy's that rely on foreign aid are struggling as donors shift funding for humanitarian demining toward active conflicts in Ukraine, Gaza and Sudan, and to more recent wars, like in Syria and Afghanistan. Today's conflicts are also driving higher defense spending, leaving less money for aid.

President Donald Trump's dismantling of the U...