In addition, we discovered that the probability distribution is dramatically shifted by varying the contact force between the tungsten microprobe and LLZO surface. Ex situ diamond-tip indentation showed significant deviation from an elastic-plastic response, suggesting that microcracking is occurring in the sample. Further, FEM analysis of the microprobe-LLZO contact suggested that plastic deformation in LLZO is unlikely. Operando LLZO cantilever bending experiments revealed that intrusion propagation is strongly influenced by compressive strain of only ~0.070%. Based on these results, we conclude that nanocracks (either pre-existing ones or those generated via external loads) are the origin of lithium-metal intrusions in LLZO and their propagation behavior can be controlled by mechanical strain. We emphasize that these microcracks are difficult to observe using standard microscopy techniques such as SEM or optical imaging and look to the development of advanced characterization methods to study