Porter was trained at the Royal Academy under the patronage of Benjamin West (1738–1820), having apparently been inspired to become a painter of battle scenes by one such belonging to Flora Macdonald (1722–90), the Jacobite heroine. In 1799 he became a founder member of the Brothers, a group of young artists wishing to establish history painting in England. After the enormous success of the equally huge history painting, The Storming of Seringapatam, Porter painted several more paintings depicting events in the Napoleonic Wars, of similar size, and thus secured a commission from Emperor Alexander I to go to St Petersburg and paint the walls of Admiralty Hall. From 1805 to 1807, he lived in St Petersburg and made two trips to Moscow, before being obliged to leave the country after the Treaty of Tilsit, in which Russia allied herself with France. His experiences were documented in his Travelling sketches, published after his return, based on letters written to a friend, Henry Caulfield (1779–1808), and illustrated with his own pictures. He excused the rather unformed nature of his work by the fact that Caulfield was dying when he was endeavouring to put the book together, and confessed that it was: