This volume is the first in a series of papers about systems approaches in complex environments, which includes the use of the collective impact model to address large-scale social problems, and the application of participant-driven MEL techniques across 17 networks of civil society organizations. It is based on the experiences of Root Change and Chemonics, two development partners working on a USAID civic engagement project in Nigeria (2013-2018), as well as hundreds of Nigerian civil society organization partners. This is the first paper in the series and aims to present a brief introduction to systems approaches in advocacy settings, the SACE theory of change, and the scope of Root Change’s work as technical lead on capacity building and measurement.