Why is the reaction between potassium (K) and chlorine (Cl) considered an oxidation-reduction reaction?

Why is the reaction between potassium (K) and chlorine (Cl) considered an oxidation-reduction reaction?
K(s) + Cl2(g) → 2KCl(s)
Chlorine reduces in size when it reacts with potassium.
Chlorine takes electrons from potassium in the reaction.
Potassium reduces in strength when it bonds with chlorine.
Potassium takes chlorine’s place in the reaction.