This synthesis paper gathers research evidence around community engagement in relation to combating jihadist influenced terrorism, including the practical role of moderate and non-violent extremist movements. The paper is divided into three sections: the first section sets out the key debates within the research literature on the challenges of engaging communities and moderate and non-violent extremist movements in the UK. This section emphasises the importance of engaging communities in combating jihadist terrorism and also highlights the key complexities and challenges involved. This section also highlights that whilst there is considerable debate and controversy about the involvement of non-violent extremist movements in counter-terrorism, there is nonetheless research evidence of the merits of including non-violent extremists in community-based approaches. Section two explores some of the key Islamist movements from an historical and ideological perspective and what the research tells us about these movements in relation to their involvement in violence and its prevention. This section particularly focusses upon our understanding of Islamist movements in relation to their involvement in perpetuating and/or combating jihadist terrorism in the UK and internationally. Section three presents research evidence of the more contemporary practical involvement of non-violent “extremist” movements, both nationally and internationally, in combating terrorism.