The　shielding　and　amplification　effects　of　multiple　inclusions　and　microcracks　on　the　tip　or　the　growth　path　of　a　main　crack　under　dynamic　loading　are　investigated　using　numerical　simulations.　The　simulations　employ　a　combined　numerical　tool　based　on　the　time-domain　boundary　element　method　together　with　the　sub-region　technique　for　multi-regions,　the　maximum　circumferential　stress　criterion　for　crack-growth　direction　and　discrete　modelling　for　the　crack　propagation.　New　elements　of　constant　length　are　added　to　the　moving　crack-tip　to　simulate　the　growth　at　an　adaptable　time-step　according　to　the　crack　propagation　criterion.　Of　particular　interest　is　the　study　of　the　effects　of　the　sizes　and　positions　of　inclusions　and　microcracks　and　the　material　combinations　on　the　dynamic　stress　intensity　factors　and　the　crack　growth　path.　The　numerical　results　demonstrate　the　crack-tip　shielding　and　amplification　effects　of　inclusions　and　micro-cracks.