In the modern context, in the United States at least, I understand the accusation of “dual loyalty” generally meaning that the accuser believes their target is not loyal to their home country, but rather Israel. I’ve heard the term thrown around most of my life, and I assumed it must have begun sometime after the formation of Israel.
However, when recently watching a video critiquing anti semitic tropes, I found out the accusation of “dual loyalty” was common during the Dreyfus affair, long before the formation of Israel or the Zionist movement. My question is, when accusing Dreyfus and other Jews of having “dual loyalty”, to what specifically did the accusers believe the accused were loyal to? Was it some imaginary “Jewish plot”, or was the term more synonymous with “disloyalty”, or just general corruption and willingness to betray France for personal gain?
Typically, the belief was of two sorts:
Jews generally were not "trustworthy", and so they were likely to be disloyal to their own country and willing to be spies for others.
Jews generally were only loyal to other Jews, be that the "global Jewish conspiracy" (or "global Zionist conspiracy" depending on the decade), and not to the countries they were in.
In the former setup, it was more about lack of love for one's country. Jews were simply portrayed as weak, or cowards, or greedy and easily bought out. This is more of what the Dreyfus Affair signified, as an example where that antisemitic assumption and bias existed.
However, the more nefarious kind was the dual loyalty to some mythical "world Jewry". You see this in things like the Protocols of the Elders of Zion, the infamous antisemitic forgery, which paints a (fake) conspiracy about Jews running the world. The Protocols were used to claim that Jews were disloyal to the countries they were in because they were only loyal to Jews, the global Jewish community, and Jewish "puppetmasters" behind the scenes. In some iterations, the "global Jewish conspiracy" only controlled part of the world, so Jews were assumed to be disloyal, and were accused of trying to place more of the world under the "control" of the Jews.
This type of theory spread far and wide, even long before the Nazis. But in modern history, one example is the Dearborn Independent published by Henry Ford (yes, that Henry Ford). There are hundreds of pages of antisemitism in the publication, with quotes like this one:
...the Jew's loyalty is to the Jewish nation; what the Jew himself refers to as his "cover nationality" may count or not as he himself elects.
And:
When one addresses Jews he knows that the Jew is always a Jew; that every Jew acknowledges every other Jew; that Jews understand each other and are loyal to each other as against "outsiders"; that they think together and act together; that they stand together for Jewish defense, no matter how just the charges brought against them. When you address Jews you address a unit, and when you discuss Jews you get a united reaction from them.
This is, of course, patently absurd. There's an old Jewish saying that two Jews in a room will have three opinions. The idea that Jews were "united" by their willingness to flout loyalty to the states they were in, on the basis of being Jewish, is nonsense. But these opinions date back decades, and sometimes centuries, and those quotes are from 1920-21 (so 100 years ago or so, and before the Nazis).
So the term was synonymous with both some loyalty to a "Jewish plot", and to Jewish "cowardice", and to Jewish "corruption", all at once.