Mpande adopted an expansionist policy in the early 1850s, initially raiding the areas surrounding the Zulu kingdom. These moves culminated in the invasion of Swaziland in 1852. The Swazi were under Zulu suzerainty, but maintained effective independence under Mswati II. According to historian Philip Bonner, Mpande wanted Swaziland to be under his control because of fears of Boer expansion from Natal. He "was intent on turning Swaziland into a physical sanctuary should he become embroiled with Natal, and was not prepared to settle for anything less than effective control". The Zulu invasion was a success to the extent that the Swazi were faced with the prospect of "disintegration and collapse". During the invasion, Mpande's eldest son Cetshwayo proved his capacities as a leader. However, the British pressured him into withdrawing, which he did quickly.