[1] At the age of thirteen, Dashwood entered the Royal Navy, being appointed as a midshipman on 9 January 1779, and embarking on board the 74-gun ship HMS Courageux, commanded by Captain Lord Mulgrave.

[2] Returning from Jamaica to England with Garnier in the Grafton, he embarked on board HMS Formidable, flagship of Sir George Rodney, acting as aide-de-camp during the Battle of the Saintes,[2] where the French fleet was beaten thanks to the innovative tactic of "breaking the line", giving Britain a weapon to wield at the Treaty of Versailles, and restoring the status quo that the British had in the West Indies to that of 1776.

[2] He distinguished himself in the Glorious First of June, at which British Admiral Richard Howe attempted to destroy a large French fleet protecting a convoy.

During the course of the engagement, Dashwood had to lash the fore top-sail yard which had been shot in the slings, to the cap, whereby the ship was enabled to wear in pursuit of the enemy.

[6] He was superseded by an officer of HMS Canada, bearing Sir John B. Warren's broad pendant, and was appointed in command of La Coquille, one of the frigates captured that day, which he sailed into Belfast and then to Plymouth.

[7] He continued serving on board Magnagnime and after contributing to the capture of some privateers, on 2 August 1799 he was promoted to the rank of commander, and appointed captain of the 18-gun ship HMS Sylph.

[2] The following year, Dashwood's command was employed on operations within gunshot distance of the French batteries in Brest harbour, and on one occasion, during a foggy night, he rescued the British frigate HMS Alcmene, after she had become grounded and began drifting among the rocks.

[8] After beating the enemy twice, Dashwood, on rejoining the fleet off Brest, was congratulated by Admiral William Cornwallis who recommended to the Board of Admiralty that he be promoted, albeit with no effect.

In consequence of not being able to tell the name of the enemy ship, his promotion was delayed, as it evidenced in the following letter from the Earl of St. Vincent, replying to Cornwallis' recommendation of Dashwood's application for a post commission: I have read your official letter with all the attention such a recital merits; but until the Board receive official information of the force, and the nation to which the vessel belongs, which the Sylph was engaged with, and adequate judgement cannot be formed of the merits of the action.

Aboard that ship he convoyed a fleet from Oporto and then proceeded to the West Indies, where he captured, on 3 April 1803, the Spanish schooner La Elizabeth, of 10 guns and 47 men.

[10]On 5 April 1805, as Bacchante was cruising off Havana, Dashwood received information that there were three French privateers lying in the harbour of Mariel, located to the westward and defended by a tower nearly 40 feet high, on the top of which were placed three long 24-pounders, and round its oval numerous loop-holes for musketry.

Accordingly, in the evening, he dispatched on that service two boats, containing about 35 seamen and marines, under the command of Lieutenant Thomas Oliver, with directions to attack and carry the fort prior to entering the harbour.

[11] While commanding HMS Franchise, a frigate of 36 guns,[d] Dashwood saw action in the West Indies, where he captured the Spanish schooner El Carmen and the Dutch armed vessel Brutus.

[13] On 1 August 1807, he parted in company with Commodore Richard Keats' squadron and sailed to the passage of the Great Belt, in order to intercept any ships carrying Danish troops crossing from Holstein to Zealand.

A squadron under his orders, consisting of the former HM Ships Franchise, Daedalus, Aurora, Reindeer and Pert, blockaded the city of Santo Domingo by taking possession of the town of Samaná, where the French were erecting batteries for their permanent establishment.

[20]During the winter of 1811, Dashwood commanded a squadron of 10 sloops and smaller vessels, in order to collect and bring home the remnant of Rear-Admiral Robert Reynold's convoy that had been prevented from passing through the Skagerrak by bad weather.

[21] In the Baltic, amidst the context of the Anglo-Swedish War, Dashwood received notice that the Swedes were fitting out eight sail of the line and five frigates at Karlskrona.

[26] After serving in the North Sea under Admiral Sir William Young, Dashwood escorted a convoy to the West Indies, whence he returned with another of equal importance.

Afterwards he took part, commanding HMS Norge of 74 guns, in the Battle of New Orleans, where he assisted Admiral Pulteney Malcolm in the debarkation of the army, being reported by Sir Alexander Cochrane.

In 1815, when at anchor in Port Royal, his ship was struck by lightning, which broke the main-topgallant-mast in three pieces, shivered the maintop-mast and brought the mizentop-mast and topgallant-mast down on to deck.