Buying people in the opposite camp to switch allegiance is an activity as old as states are. In antiquity, bribes were often given to shift the loyalty of allies from one camp to another. The Byzantines famously bribed the Turks to fight as mercenaries in their internal wars, thus giving them a way in, and even lured the Fourth Crusade away from their Holy Land targets to Constantinople with catastrophic results when the Western knights decided that Constantinople was an easier and richer prize for them than Jerusalem. Before the Bosworth battle, the Stanley family negotiated to switch loyalty from the Yorks to the Lancasters- for profit.
Public corruption is a modern phenomenon (being defined in relation to modern public office and its obligations towards the citizenry as undue private profit from public office abuse) but treason for profit, which we now call ‘strategic corruption’ is as old as government. The U.S. Constitution (Article I, Section 9, Paragraph 8) includes a foreign emoluments clause, a provision that generally prohibits federal officeholders from receiving any gift, payment, or other thing of value from a foreign state or its rulers, officers, or representatives (an unsuccessful attempt existed to use this against Trump).
Treason is bad, even worse than corruption, it requires harsh penalties and carries a serious stigma. Flagging the corruption part of treason makes little sense, though. Separating what is corrupt (Qatar Gate) from opportunistic behavior taking advantage of loose regulation (the London City or Luxembourg law firms laundering money) and from plain treason may allow more efficient policy responses. That would also prevent the complete merging of corruption with the security debates in Academia, which may turn out for the mutual academic benefit. We study all these phenomena in BridgeGap, but try to come up with more rigorous categorizations than lumping in one term the strategy of one country with the corruption of another.
Further quality reading of Branko Milanovic here.
