The timing of spring break-up of landfast sea ice has become less predictable in recent years due to changes in the Arctic climate, which has implications for the traditional lifestyle of Inuit and shipping operations. To study the processes related to landfast ice break-up, meteorological and oceanographic data were collected in Admiralty Inlet, NU in May-June 2019. Numerical experiments using a finite element model (FEM) demonstrated the effects of environmental stresses, ice material properties, and leads on sea ice deformation prior to break-up. Modelled stress magnitudes were well below estimates of tensile yield stress, implying that large-scale ice fracture does not occur under typical conditions. Rather, field data and FEM output suggest the deterioration of ice strength and development of cross-inlet and shore leads preconditioned the ice to allow relatively low wind and current forces to initiate a break-out event in Admiralty Inlet on June 27, 2019.