Henry himself married Henrietta Jermyn, who bore him two children, John Gage and Mary Gage.
He became a professional soldier, and being a Catholic, served on the Spanish side in the long-running conflict in the Low Countries for most of his life. He was known for his ability and was described as “a complete soldier and a wise man.”. He was also noted for his piety (he attended Mass daily) and in the later years in the Low Countries and in England had as his chaplain the Jesuit Peter Wright, later to be sentenced to death on the evidence of Henry's own brother Thomas Gage, a Catholic renegade.
Responding to the King's summons in the English Civil War, he returned to England and went to the Royalist headquarters at Oxford. In September 1644 an appeal for military assistance came from Basing House. This was the seat of the Catholic Marquis of Winchester, the largest private residence in England, located at Old Basing, by the River Loddon (a tributary of the River Thames), forty miles away from Oxford and twelve miles south of Reading, Berkshire. The site covered fifteen acres within a mile and half of enclosing walls and earthworks. The 'Old House' was a medieval fortress on a defensive mound and next to it stood the palatial 'New House', five storeys high and with 380 rooms. In November 1643 it had been placed under siege by Sir William Waller's Parliamentary troops. Though this first siege lasted only nine days, in June 1644, the house was besieged again, this time by Colonel Richard Norton, whose use of heavy mortar bombardment led in September to the Marquis's garrison asking Royalist forces at Oxford, forty miles away, for help. There the commander Colonel Henry Gage assembled a relief force consisting of Colonel Hawkins's regiment, a hundred volunteers and various servants. Disguised on the road as Parliamentarians, they managed to break through to Basing House, replenishing the garrison's ammunition and food and then escaped by night back to Oxford, swimming their horses across the Kennet and the Thames. For this Colonel Gage received a knighthood. Less than a fortnight after Colonel Gage's relief, Colonel Norton resumed the siege, which seven weeks later Colonel Gage again relieved. The house was eventually to be heavily bombarded, looted to the tune of some £200,000 and then systematically demolished by Oliver Cromwell in 1645. On Christmas Day 1644 the King made Gage Governor of Oxford, in place of the Catholic Sir Arthur Aston (1590-1649), thus earning in Aston a bitter enemy who made every effort to discredit him and undermine his authority. The time for this mischief was short, however. The following month Gage was killed in a skirmish at Culham Bridge near Abingdon on January 11 1645. He was given an impressive military funeral at Christ Church Cathedral, Oxford, where he is buried. His memorial is in the Lucy Chapel, off the South Transept. The inscription reads:
For the family tree of the Gages for this period:
For the story of the Basing House siege: