Editing John, King of England (section)

===War with the barons===
{{Main|First Barons' War}}
[[File:King John's campaign 1215-6.png|thumb|upright=1.13|alt=A map of England showing King John's march north and back south with solid black and dashed arrows.|John's campaign from September 1215 to March 1216]]
The rebels made the first move in the war, seizing the strategic [[Rochester Castle]], owned by Langton but left almost unguarded by the archbishop.<ref name="TurnerP192">Turner, p. 192.</ref> John was well prepared for a conflict. He had stockpiled money to pay for mercenaries and ensured the support of the powerful [[marcher lords]] with their own feudal forces, such as William Marshal and [[Ranulf de Blondeville, 6th Earl of Chester]].<ref>Turner, p. 191.</ref> The rebels lacked the engineering expertise or heavy equipment necessary to assault the network of royal castles that cut off the northern rebel barons from those in the south.<ref>Turner, p. 191; Barlow, p. 354.</ref> John's strategy was to isolate the rebel barons in London, protect his own supply lines to his key source of mercenaries in Flanders, prevent the French from landing in the south-east, and then win the war through slow attrition.<ref name=TurnerP192/> John put off dealing with the badly deteriorating situation in North Wales, where Prince Llywelyn was leading a rebellion against the 1211 settlement.<ref>Rowlands, pp. 286–287.</ref>

John's campaign started well. In November John retook Rochester Castle from rebel baron [[William d'Aubigny (rebel)|William d'Aubigny]] in a sophisticated assault. One chronicler had not seen "a siege so hard pressed or so strongly resisted", whilst historian Reginald Brown describes it as "one of the greatest [siege] operations in England up to that time".<ref>Turner, p. 192 citing Brown, pp. 10–11; Turner, p. 193.</ref> Having regained the south-east John split his forces, sending William Longespée to retake the north side of London and East Anglia, whilst John himself headed north via [[Nottingham]] to attack the estates of the northern barons.<ref name="TurnerP193">Turner, p. 193.</ref> Both operations were successful and the majority of the remaining rebels were pinned down in London.<ref name=TurnerP193/> In January 1216 John marched against Alexander II of Scotland, who had allied himself with the rebel cause.<ref name="DuncanP267">Duncan, p. 267.</ref> John took back Alexander's possessions in northern England in a rapid campaign and pushed up towards [[Edinburgh]] over a ten-day period.<ref name=DuncanP267/>

The rebel barons responded by inviting Prince Louis of France to lead them: Louis had a claim to the English throne by virtue of his marriage to [[Blanche of Castile]], a granddaughter of Henry II.<ref name="TurnerPP191-2">Turner, pp. 191–192.</ref> Philip may have provided his son with private support but refused to openly support Louis, who was excommunicated by Innocent for taking part in the war against John.<ref name=TurnerPP191-2/> Louis' planned arrival in England presented a significant problem for John, as Louis would bring with him naval vessels and siege engines essential to the rebel cause.<ref>Barlow, p. 356.</ref> Once John contained Alexander in Scotland, he marched south to deal with the challenge of the coming invasion.<ref name="DuncanP267"/>

Louis intended to land in the south of England in May 1216, and John assembled a naval force to intercept him.<ref name=TurnerP193/> Unfortunately for John, his fleet was dispersed by bad storms and Louis landed unopposed in [[Kent]].<ref name=TurnerP193/> John hesitated and decided not to attack Louis immediately, either due to the risks of open battle or over concerns about the loyalty of his own men.<ref name="TurnerP193"/> Louis and the rebel barons advanced west and John retreated, spending the summer reorganising his defences across the rest of the kingdom.<ref name="TurnerP194">Turner, p. 194.</ref> John saw several of his military household desert to the rebels, including his half-brother William Longespée. By the end of the summer the rebels had regained the south-east of England and parts of the north.<ref name=TurnerP194/>