On 29 August 2013 the UK House of Commons inflicted the first defeat on a PrimeMinister over a matter of war and peace since 1782. Recalled to debate and vote on UK intervention in Syria, the Commons humbled the government and crucially impacted the development of UK foreign policy. This article places that vote, and the developments leading to it, in the context of the role of parliaments in security policy and explores the relationships between parliamentary influence, leadership, intra-party and intra-coalition politics, and public opinion. From an in-depth analysis of leaders' statements and parliamentary debate, we find a combination of intra-party politics and party leadership were most significant. An additional factor -the role of historical precedent -was also important. Our analysis explores the fluidity and interconnectedness of the various factors for parliamentary influence in foreign policy and offers directions for future theoretical development and empirical research.Keywords: foreign policy analysis; decision-making; UK foreign policy; parliaments.
2'A leader humbled, a nation cut down to size ' (Rachman 2013 This was an unusual case of a parliament defying a PM's preference on a decision to deploy military force. This vote was unprecedented in UK politics and challenges conventional wisdom that Westminster has little influence in security policy. Yet this case also resembles instances of parliamentary influence elsewhere and the factors that explain this vote are consistent with other cases. After a brief description of the backdrop to the vote, we establish the theoretical context of parliaments' role in security policy, setting out the general expectation that parliaments are not particularly influential. At the heart of the article we consider -through a consolidation of previous research -factors that facilitate parliamentary influence in security policy and examine the impact they each had in the Syria vote. In concluding, we use this case to suggest directions for future research. Our aim is to explain this particular vote and to advance research and understanding about the role of parliaments in security policy. We ground our analysis of parliamentary influence in a conceptualisation of political dynamics focusing on group and individual actors from a decision-making perspective. From this wide-ranging research, we consolidate and specify several facilitating factors for parliamentary influence in security policy. They include:• Institutional powers of parliament;
8• Public opinion;• Cabinet type;• Intraparty factions; and• Prime Ministerial (PM) leadership style.These factors can, and often do, act together, but here we present the logic of each separately. Furthermore, none are deterministic; there are caveats to the logic of each of them. Following a comparative, general analysis of factors for parliamentary influence in foreign and security policy, we apply these to the Syria vote.