When was the first joint operation in military history?

Answer 1

We have no knowledge of what the first of anything is, as our records go back only so far.

Presumably 'joint' means a joint effort by two or all of army, navy, air force. Early military activities did not really discriminate between army and navy. As an example the rowers in the Iliad became soldiers when ashore. It was not until there was a definite establishment of navies and armies that such a phrase as joint operation became valid, and consequently 'first' has little meaning.

However an early example of a joint operation was the Thermopylai-Artemesion operation during the Persian invasion of Greece in 480 BCE. The Greek defence strategy was to eliminate the threat of the Persian war fleet. As it was superior to their own war fleet, they needed to engage it in narrow waters to neutralise the numbers and better ships. So they selected the strait between the mainland and island of Euboia. They then blocked the land route with a small force at the pass of Thermopylae to force the Persians to attempt to outflank it with their navy, which would allow a sea battle in the strait.

This was therefore a good early example of a joint effort of naval and land forces to achieve a desired effect. Unfortunately the Greeks got the worst of the sea engagement, so it was not a successful one in achieving that desired effect.