In 1806 he was first-lieutenant of the _Siren_, a little sloop-of-war in the Mediterranean service. On one occasion when Captain Smith, the commander of the _Siren_, had gone on shore, young Lieutenant Macdonough saw a boat from a British frigate lying in the harbor row up to an American brig a short distance off, and afterward put out again with one more man in her than she had originally. This looked suspicious, and Macdonough sent to the brig to ascertain the reason, with the result that he found that an American had been impressed by the English captain’s orders. Macdonough quietly lowered his own boat and put after the heavy cutter, which he soon overhauled. Although he had but four men with him, he took the man out of the cutter and brought him on board the _Siren_. When the English captain heard, or rather saw, what had occurred--it was right under the bow of his frigate that the affair took place--he waxed wroth, and, calling away his gig, he rowed to the _Siren_ to demand an explanation. The following account of the incident is quoted from the life of Macdonough in Frost’s _Naval Biography_: “The Englishman desired to know how Macdonough dared to take a man from one of his Majesty’s boats. The lieutenant, with great politeness, asked him down into the cabin; this he refused, at the same time repeating the same demand, with abundance of threats. The Englishman threw out some threats that he would take the man by force, and said he would haul the frigate alongside the _Siren_ for that purpose. To this Macdonough replied that he supposed his ship could sink the _Siren_, but as long as she could swim he should keep the man. The English captain said to Macdonough: “‘You are a very young man, and a very indiscreet young man. Suppose I had been in the boat--what would you have done?’ “‘I would have taken the man or lost my life.’ “‘What, sir! would you attempt to stop me, if I were now to attempt to impress men from that brig?’ “‘I would; and to convince yourself I would, you have only to make the attempt.’ “On this the Englishman went on board his ship, and shortly afterward was seen bearing down in the direction of the American vessel. Macdonough ordered his boat manned and armed, got into her himself, and was in readiness for pursuit. The Englishman took a circuit around the American brig, and returned again to the frigate. When Captain Smith came on board he justified the conduct of Macdonough, and declared his intention to protect the American seaman.” Although Macdonough was very young, and his rank but that of a lieutenant, people who knew him were not surprised to hear that he had been appointed to take command of the little squadron on Lake Champlain. These vessels were built of green pine, and almost without exception constructed in a hurried fashion. They had to be of light draught, and yet, odd to relate, their general model was the same as that of ships that were expected to meet storms and high seas.