Isn't this pretty much an open secret? Doesn't everyone spy on everyone else, even when they're nominally allies?
It's telling that Spain merely expelled these people, rather than locking them up and/or torturing them for information. I'm sure there's some sort of gentlemen's agreement that this is what you do when you catch an ally's spies.
It's telling that Spain merely expelled these people, rather than locking them up and/or torturing them for information. I'm sure there's some sort of gentlemen's agreement that this is what you do when you catch an ally's spies.