The paper addresses the problem of quantifying and assessing the effectiveness of icebreaker operations in ice management (IM) using a high-fidelity simulator. The numerical model includes an accurate geometric representation of an icebreaker, a cylindrical protected structure, and a synthetic ice environment. A set of key performance indicators (KPIs) are defined and proposed to quantify the effectiveness of IM strategies for protecting the downstream structure. This give better insight into which IM strategies are more effective with respect to different objectives for certain conditions, thereby enabling better planning and guidance of icebreaker operations. The results from a selection of the simulations performed with nearly 100% ice concentration are presented. This will illustrate the methodology using the different KPIs to quantify the effectiveness and highlight differences between the different IM strategies. From the simulations we see that all patterns have strengths and weaknesses; some KPIs are consistent while others are changing with the ice drift velocity.