Bangladesh, Feb. 1 -- Gentry Beach, a Texas-based businessman and longtime confidante of Donald Trump Jr., has embarked on a self-styled diplomatic mission that could have serious geopolitical repercussions. Despite holding no official position in the Trump administration, Beach has been engaging with controversial world leaders, making authoritative statements, and positioning himself as a key advisor to President Trump. His recent visits to Pakistan and Bangladesh, where he met with Islamist figures and anti-Trump activists, raise pressing questions about his real motives and the implications of his actions on US foreign policy.

Could his unauthorized dealings destabilize South Asia or jeopardize Trumps carefully crafted global stance?...