As civil war broke out in 1642, both sides claimed to be acting defensively: the war was defined in terms of what it was intended to prevent, rather than what it was hoped it would achieve. Partisans sought military strength in order to secure a safe peace, with the result that there was a contrapuntal relationship between fighting and talking. But there was an inherent difficulty in this: the increasing demands of the military mobilizations put pressure on the initially defensive claims. In summer 1642 there had been tussles for control over local military resources and in the autumn one significant pitched battle, which proved inconclusive. Early in 1643, these military considerations looked rather different and rather more challenging. As peace negotiations were about to start in Oxford, Parliament was also preparing for a sustained campaign on several fronts. Innovative financial and military demands forced Parliament to claim powers that were difficult to justify in legal and constitutional terms acceptable before the war. This pressure for administrative innovation, built into the effort to secure a peace by fighting a war, generated new claims to political legitimacy – either in the sense of novel uses of pre-existing forms of argument, or entirely new political and religious claims. As the practical costs of military mobilization escalated, in other words, so, too, did the ideological claims of the cause, with the consequence that the campaign might come to seem quite different from the one being championed in January or even September 1642.