Gascoigne was killed at the battle of Marston Moor on the 2nd of July 1644, in the twenty-fourth year of his age, and his untimely death was doubtless the cause that delayed the publication of a discovery which anticipated, by twenty years, the combined work of Huygens, Malvaison, Auzout and Picard in the same direction.
At Marston Moor on the 2nd of July he commanded all the horse of the Eastern Association, with some Scottish troops; and though for a time disabled by a wound in the neck, he charged and routed Rupert's troops opposed to him, and subsequently went to the support of the Scots, who were hard pressed by the enemy, and converted what appeared at one time a defeat into a decisive victory.
The movements of Manchester of ter Marston Moor were marked by great apathy.
Until his fiery energy made itself felt, hardly any army on either side actually suffered rout; but at Marston Moor and Naseby the troops of the defeated party were completely dissolved, while at Worcester the royalist army was annihilated.
He commanded a troop of horse in Scotland in 1639; was involved in army plots in 1641, for which he was committed to the Tower, but escaped abroad; and on the outbreak of the Civil War returned to England and served with Prince Rupert, being present at Marston Moor, the second battle of Newbury and Naseby.