Complex sentence: From 1846 he renewed his policy of hostility to the British and allied himself with the Sikhs; but after the defeat of his allies at Gujrat on February 21,1849 he abandoned his designs and led his troops back into Afghanistan.
Split into simpler sentences: From 1846 he renewed his policy of hostility to the British and allied himself with the Sikhs. However, after the defeat of his allies at Gujarat on February 21,1849, he abandoned his designs and led his troops back into Afghanistan.