Telegraphy increased the centralization of foreign ministries. When ambassadors were months away from their political superiors, they were often forced to take pressing and important decisions before they could receive their instructions. In such circumstances, they exercised enormous power, sometimes even acting as policymakers in their own right. In contrast, telegraphy circumscribed the independence of diplomats. It reduced the pressure of difficult decisions, which diplomats had previously faced without ready access to advice from their superiors. Yet, it also diminished the prestige and the power of diplomatic representatives. Their function changed. Whereas diplomats had once received autonomy because the sending of instructions to respond to every eventuality was slow and cumbersome, they now, in the age of the telegraph, were prized in part for their inefficiency. They provided an extra layer of expertise and slowed the policymaking process, thereby reducing the chances of a catastrophic error.
The formation and implementation of foreign policy can be a high-risk endeavor. In an environment in which miscalculation can lead to a disastrous war or diplomatic defeat, foreign ministries tend to be skeptical of radical changes and untried methods. Yet, foreign ministries did cautiously adapt to the telegraph. In 1859, Britain's Foreign Office hired resident clerks to handle telegrams received after the close of business. The U.S. Department of State established a telegraph office in 1866, a few months after the permanent establishment of transatlantic telegraphy. Diplomats learned to write more concisely in order to reduce telegraph expenses, which typically increased with the length of messages. Foreign ministries made more frequent use of codes in an (often fruitless) effort to keep the contents of their telegrams secret from spies.
In the late 20th and early 21st centuries, new technologies of communication--especially networked computers and fiber optic cables (which carried light rather than electricity)--marked the end of diplomacy by telegraph. Yet, the telegraph deserves to be remembered as the technology that brought diplomacy into the high-speed age of electricity.