In early 1793 he wrote to Charles O'Hara, seeking passage to Gibraltar, of which the latter was lieutenant-governor and sailed aboard the "Resistance" with Lord St Helens, ambassador to Spain. After France declared war on Great Britain and the Dutch Republic on 1February 1793, the British fleet under Admiral Samuel Hood assembled at Gibraltar. On his arrival there, Graham volunteered and went with the navy to Toulon, where he acted as "aide-de-camp" to Lord Mulgrave and fought in the defence of the town. According to Sir Gilbert Elliot, Graham "left the highest character possible both for understanding and courage".