This model provides a means to assess whether the experimental observations are consistent with fracture-governed dendrite propagation. If filament propagation is driven purely by mechanical fracture, the plating-induced pressure 𝑃𝑃 that would be inferred from experiments would match the fracture stress expected from an ex-situ test (called 𝜎𝜎 𝑐𝑐𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑎𝑎 ). If, on the other hand, propagation is governed largely by chemical degradation, as would be the case for failure via electronic leakage, then the inferred 𝑃𝑃 should be much lower than 𝜎𝜎 𝑐𝑐𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑎𝑎 . We estimate 𝜎𝜎 𝑐𝑐𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑎𝑎 by drawing on the analysis of Beuth et al. , who studied propagation of through-cracks in a thin plate of the geometry in Fig. . Applying their analysis to the 90 μm thick LLZTO disc studied here (detailed further in Methods) yields 𝜎𝜎 𝑐𝑐𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑎𝑎 values between 65 and 120 MPa (for LLZTO fracture toughness, KIC, of 1-2 MPa√𝑚𝑚) . The plating-induced pressure 𝑃𝑃 is independently inferred from the change in filament propagation angle under a known load. From Fig. , the measured angles of 𝛽𝛽 = 36° and 𝜃𝜃 = 71° under an applied load of 70 MPa yield 𝑃𝑃 = 115 MPa, which is indeed similar in magnitude to 𝜎𝜎 𝑐𝑐𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑐𝑐𝑎𝑎𝑎𝑎 . This comparison supports the conclusion that dendrite propagation is a fracture process in which the plating-induced pressure 𝑃𝑃 is approximately the critical stress required for fracture.