The man commanding the Crown Forces in New Ross on 5th June 1798 was Dublin born General Henry Johnson.
Below is a brief biography of the man.
Johnson, Sir Henry, Bart., G.C.B., General, was born in Dublin in 1748, entered the army in 1761, and rose through the several grades — Captain, 1763; Lieutenant-Colonel, 1778; Colonel, 1782; Major-General, 1793; General, 1808. He commanded a battalion of Irish light infantry in the American Revolutionary War, and was severely wounded; and while in command at Stony Point was surprised by General Wayne on the night of the 15th July 1779, and made prisoner with his whole force. In 1782 he married an American lady, and returned to England after the capture of Yorktown. During the Insurrection of 1798 he commanded a division of the army in the County of Wexford, and on 5th June defended New Ross. It was attacked early in the morning of that day by an overwhelming body of insurgents under Bagenal Harvey, who were at first successful, driving most of General Johnson’s troops out of the town, but not following up their success, and abandoning themselves to pillage and inebriety, were in the afternoon obliged to retreat to Slievecoillte. Musgrave places the insurgent loss at 2,500, while Johnson’s casualties numbered altogether but 227. In the engagement General Johnson displayed signal bravery, and had two horses shot under him. Lord Cornwallis thus writes of him: “Johnson, although a wrong-headed blockhead, is adored for his defence at New Ross, and considered as the saviour of the south.” General Johnson received a baronetcy in 1818, and died 18th March 1835, aged about 87, being succeeded in the baronetcy by his son, a distinguished Peninsular officer, who survived until 27th June 1860.
Source: A Compendium of Irish Biography, 1878