Consider the following statements:

(1) The dielectric medium between the plates of a parallel plate capacitor lowers the potential difference between the plates without a battery,

(2) The maximum electric field that a dielectric can withstand without having it to breakdown is called dielectric strength.

Both 1 and 2 are true, 2 is not a correct explanation of 1

When a dielectric is inserted, the electric field inside the capacitor decrease decreasing the potential between the two plates of capacitor. However, this does not impact the dielectric strength in any way.