Returning to England with a well-deserved reputation, he was in the employment of Charles I in various military capacities. As "Sergeant-Major-General" of the infantry, he went north in 1639 to organize the defence against the expected Scottish invasion. Here his duties were as much diplomatic as military, as the discontent which ended in the Civil War was now coming to a head. In the ill-starred Bishops' Wars, Astley did good service to the cause of the king, and he was involved in the so-called "Army Plot".