Most brittle solids of engineering and scientific interest have heterogeneous microstructures— comprised of a polycrystalline matrix interspersed with micro-scale defects such as cracks, second-phases, precipitates, grain boundaries, and pores. These heterogeneities (“defects”) are often initiators of micro-cracking which results in damage-induced softening and non-linearity in stress-strain response. The behaviour under dynamic loading is particularly sensitive to the initial defect population because of enhanced microcrack nucleation as compared to crack growth. The stress intensity factors (SIFs) at crack tips are also very sensitive to the material’s microstructure, i.e., the size, orientation, and three-dimensional spatial distribution of nearby inhomogeneities. A modeling approach that captures the influence of a crack’s neighbours should result in improved estimates of brittle fracture driven micro-crack growth and ensuing damage. In this work we consider the effect of the heterogeneities in the local environment of a crack by analytically predicting the elastic interaction fields between the crack and its neighbors. Our model further captures the effect of increasing compliance of the material at the macroscale by using a crack-matrix-effective medium approach. A thermodynamically consistent damage model which accounts for the statistics of size, spacing (number density) and orientation of the cracks is employed and is used to predict an anisotropic increment in compliance at each time step.