Operation Torch succeeded in its initial objectives: Allied forces established footholds in Morocco and Algeria within the first days of the invasion, Vichy French forces ceased resistance relatively quickly, and the operation provided the base from which the eventual Allied campaign across North Africa would proceed. The specific relationship between the intelligence that Baker contributed to and the operational success of Torch cannot be established with the precision that would be required to make a direct causal claim. What can be established is that she was an active participant in the intelligence networks that were essential to the planning, and that she was recognized for that participation by the people with the authority and the information to assess it.
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## What Invisible Ink Was and Is
The invisible ink that Baker used to conceal intelligence on her sheet music pages was part of a tradition of covert communication that predates the Second World War by centuries. The practical problem that invisible ink addresses — how to transmit information past a hostile reader who controls the medium of transmission — is as old as the need for secret communication itself.
The ancient Greeks and Romans had formulations of invisible ink. Steganography — the art of hiding messages within apparently innocuous material — was described in ancient texts. During the American Revolution, George Washington’s intelligence networks used various formulations of invisible ink for communication between agents and headquarters. By the First World War, the development of invisible ink formulations and the methods for detecting them had become a significant area of competition between intelligence services.