His regiment served with Marshal Staremberg in November 1710 at the battle of Villa Viciosa, where his bravery attracted the notice of John Campbell, 2nd Duke of Argyll, who advanced him to the post of major, and became his friend.
He was at Mombris in Catalonia in October 1709, when he addressed some lines to John Creed of Oundle in Northamptonshire, and during the winter of 1712–13 he was writing to the Campbells from Menorca.
Edmund Curll printed for Pack in 1719 The Life of T. P. Atticus, with remarks, translated from the Latin of Cornelius Nepos; and in 1735 there appeared The Lives of T. P. Atticus, Miltiades, and Cimon, with remarks, When Curll issued in 1725 a volume called Miscellanies in Verse and Prose, written by the Right Honourable Joseph Addison, he added to it an essay on the Roman elegiac poets, by Pack, which seems to have originally appeared in 1721.
Many versions from the Latin poets were included in the Miscellanies of Pack: translations from Tibullus and Propertius, and imitations of Horace and Virgil, with poetic epistles to his friends.
In March 1719 Curll advertised a poem by Pack, entitled Morning; and he printed in 1720 a tale called Religion and Philosophy, with five other pieces.
Pack's prologue to Sewell's Tragedy of Sir Walter Raleigh, and his epilogue to Thomas Southerne's The Spartan Dame, were admired.