To test the hypothesis that localized microstructural defects initiate lithium intrusions, we engineered controlled defects into the surface of the LLZO. The most consistent method of initiating lithium intrusions was by damaging the LLZO surface via microprobe loading. Figure shows the change in the cumulative distribution function between the 0.1 and 5 mN load conditions for n = 11 and n = 23 experiments performed, respectively. There is a clear distinction between the two loadings, with the higher loading force decreasing d0 (characteristic diameter at which intrusion occurs) from 11 ± 2 µm to 4.2 ± 0.6 µm. Furthermore, d0 for the 5 mN contact is similar in size to the estimated contact region of the tungsten probe (discussed later). In addition, SEM images in Figure confirm the substantial decrease in whisker size at failure, with electrochemical data for all experiments shown in Figure . We observe that this effect is present regardless of whether the probe contact force is persistent through the entire plating process (orange circular points) or if the probe first contacted the surface at high force, retracted, and then re-contacted to the surface at < 0.1 mN in the same location (orange squares). This finding implies that the higher contact force causes irreversible damage to LLZO, leading to changes in the intrusion behavior. We note that our measurement of the contact force does not include the lateral component (sliding force) but only the surface normal component.