When Thomas Wong set foot in the United States Embassy in Beijing this summer for a new diplomatic posting, it was vindication after years of battling the State Department over a perceived intelligence threat ¡ª himself.

Diplomatic Security officers had informed him when he joined the foreign service more than a decade ago that they were banning him from working in China. In a letter, he said, they wrongly cited the vague potential for undue ¡°foreign preference¡± and suggested he could be vulnerable to ¡°foreign influence.¡±

Wong had become a U.S. diplomat thinking that China was where he could have the greatest impact. He had grown up in a Chinese-speaking household and studied in the country. And as a graduate of West Point who had done an Army tour in the Balkans, he thought he had experience that could prove valuable in navigating relations with the United States¡¯ greatest military and economic rival.