Arsthbt

Encyclopedia Britannica says,

In their modern form, vectors appeared late in the 19th century when Josiah Willard Gibbs and Oliver Heaviside (...) independently developed vector analysis to express the new laws of electromagnetism discovered by ... James Clerk Maxwell.

The phrase "in their modern form" suggests vectors were perhaps
used earlier in other forms. There seems to be no deep mathematical
idea needed for vectors to be "invented" and used much earlier.
Can anyone suggest some earlier uses of what we now call vectors?
E.g., did Newton use vectors?

This question was actually discussed on this site several times, for example here:
When was the vector notation in physics and other sciences first introduced?
It indeed looks strange to modern people but this simple idea came so late late.
Maxwell never uses vectors in his Treatise on electricity and magnetism,
which makes his notation somewhat clumsy.

In fact the idea had a predecessor: quaternions. Yes, quaternions were invented before vectors:-) And Newton did not use vectors in the explicit form.

Instead people thought in very "roundabout", complicated ways about subjects which we routinely treat with vectors nowadays. A striking example is the famous theorem of Apollonius, about "equivalence of excentric and epicycle". Motion on epicycle means that a point moves on a circle around the center (E), while the planet moves on another circle (of smaller radius) around this point. Excentric means that the planet moves on a circle of large radius whose center is different from E, and this center rotates about E (on a circle of small radius).

To us it seems completely evident that these two things are the same. If you look into
Apollonius proof of this, you see that he really proves commutativity of vector addition. And Ptolemy prises Apollonius for this.