Due to its geography, what was the most vulnerable path to invasion into the Indian subcontinent

The most vulnerable way to invade the Indian subcontinent was from the south.

Explanation:

The south side of the Indian subcontinent is formed by a peninsula, which is a piece of land surrounded by water on all sides, which facilitates the execution of invasions on that side of the subcontinent, mainly by nations that have an efficient naval power. The north side, however, does not have so many advantages for invocation, because it is composed of the Himalayan mountain range that is established as a barrier, which in a way, protects the subcontinent.