On the 3d of September, a fourth and last attack was made on Tripoli by the gunboats, aided by all the other vessels. The Turkish boats did not wait, as before, to be assaulted off the town, but, accompanied by the galleys, they placed themselves under Fort English, and a new battery that had been built near it, with an intention to draw the American shot in that direction. This change of disposition induced Preble to send Captains Decatur and Somers, with the gunboats, covered by the brigs and schooners, into the harbor’s mouth, while the ketches bombarded more to leeward. On this occasion, Somers was more than an hour hotly engaged, pressing the enemy into his own port.

The season was now drawing near a close, and the arrival of reinforcements from America had been expected, in vain, for several weeks. It was during this interval that a plan for destroying the enemy’s flotilla, as it lay anchored in his innermost harbor, was conceived, and preparations were soon made for putting it in execution. The conception of this daring scheme has been claimed for Somers himself, and not without a share of reason. There existed between him and Decatur a singular professional competition, that was never permitted, however, to cool their personal friendship. The great success of the latter, in his daring assaults, stimulated Somers to attempt some exploit equally adventurous, and none better than the one adopted then offered. The five attacks made on Tripoli, with the vigorous blockade, had produced a sensible effect on the tone of the bashaw, and it was hoped that a blow as appalling as that now meditated, might at once produce a peace. The delicacy that a commander would naturally feel about proposing a service so desperate to a subordinate, renders it highly probable that the idea originated with Somers himself, who thus secured the office of endeavoring to execute it. It is proper to add, however, that Com. Preble says the project had long been in contemplation, though he does not say who suggested it. The plan was as follows: The ketch that had originally been taken by Decatur in the Enterprise, and in which he had subsequently carried the Philadelphia frigate, was still in the squadron. She had been named the Intrepid, for the brilliant occasion on which she had first been used, but had since fallen from her high estate, having latterly been employed in bringing water and stores from Malta. This craft had been constructed for a gun vessel by the French, in their expedition against Egypt; from their service she had passed into that of Tripoli; had fallen into the hands of warriors from the new world; by them she had been used in one of the most brilliant exploits of naval warfare, and was now about to terminate her career in another, of the most desperate and daring character. It was proposed to fit up the ketch in the double capacity of fire-ship and infernal, and to send her into the inner harbor of Tripoli, by the western passage, there to explode in the very centre of the vessels of the Turks. As her deck was to be covered with missiles, and a large quantity of powder was to be used, it was hoped that the town and castle would suffer, not less than the shipping. The panic created by such an assault, made in the dead of night, it was fondly hoped would produce an instant peace, and, more especially, the liberation of the crew of the Philadelphia. The latter object was deemed one of high interest to the whole force before Tripoli, and was never lost sight of in all their operations.

Com. Preble having determined upon his plan, Somers received the orders to commence the preparations; a duty in which he had the advice and assistance of Decatur, Stewart, and the other commanders of the squadron; for all these ardent and gallant young men felt a common sympathy in his daring, and an equal interest in his anticipated triumph. The first step was to prepare the ketch for the desperate service in which she was to be engaged. With this object a small apartment was planked up in the broadest part of her hold, or just forward of the principal mast; this was rendered as secure as was believed necessary against accidents. Into this room a hundred barrels of gunpowder were emptied in bulk. A train was led aft to a cabin window, through a tube, and, by some accounts, another was led into the fore-peak. A port-fire, graduated to burn a certain number of minutes, was affixed at the end of the train, and a body of light, splintered wood was collected in another receptacle abaft the magazine, which was to be set on fire, with the double purpose of making certain of the explosion, and of keeping the enemy aloof under the apprehension of its flames. On the deck of the ketch, around the mast and immediately over the magazine, were piled a quantity of shells of different sizes with their fuses prepared, in the expectation that the latter would ignite and produce the usual explosion. The number of these shells has been variously stated at from one hundred and fifty to two hundred and fifty, the size ranging from nine to thirteen and a half inches. The best information, however, would seem to place the number below two hundred. Some accounts give the quantity of powder as high us fifteen thousand pounds, which was probably near the truth.

Two boats were to accompany the ketch, one an exceedingly fast rowing four-oared boat, being lent for the purpose by the Siren, and the other a six-oared cutter of the Constitution. The service requiring but few men, no more were employed than were necessary to pull the two boats. To have gone in with a single boat would have been unnecessarily hazardous, as a shot might have disabled her, while the chances of escape were nearly doubled by adding a second, at the same time that the additional men did not more than make an ordinary crew for a Mediterranean craft of the size of the Intrepid. A second officer, however, was thought necessary, and Lieut. Henry Wadsworth, of the Constitution, volunteering, his offer was accepted. Mr. Joseph Israel, of the same ship, who had just been promoted, was also anxious to be of the party, but Com. Preble deeming his assistance unnecessary, permission to go was refused him. Thus it was intended that the adventurers should be limited to twelve, of whom ten were common seamen, one a lieutenant, and the other a commander; or Somers himself.

It now became necessary to obtain volunteers for the Siren’s boat, and a call for this purpose was made by Somers on the crew of his own vessel, the Nautilus. Notwithstanding the desperate character of the service, when the want was stated to the people of this little vessel every man in her offered himself to go. This compelled their superior to make a selection. The other six seamen were obtained from the Constitution, and were chosen, it is believed, by Mr. Wadsworth, under the supervision of the ship’s first lieutenant, who at that time was the late Capt. Gordon. The four men belonging to the Nautilus were James Simms, Thomas Tompline, James Harris and William Keith; all seamen rated. Mr. Wadsworth took with him from the Constitution William Harrison, Robert Clark, Hugh M’Cormick, Jacob Williams, Peter Penner and Isaac W. Downes, all seamen rated also.

Several days were necessary to complete all these arrangements, more especially to equip the ketch in the manner described, and the action of the 3d had taken place even after the Intrepid was ready. Somers made one or two attempts to go in before the night finally selected, but they were abandoned on account of the lightness of the air. At length there were appearances in and about the harbor that induced him to think that the movements of the fire-vessel were distrusted, and, fearful of detection, he decided to go in on the night of the 4th September, if the thing were at all practicable.

Several interviews had taken place between Preble and Somers in the course of the preparations for the attempt. On one occasion the commodore burnt a port-fire in order to ascertain its time, and when it was consumed he asked Somers if he thought the boats could get out of reach of the shells within the few minutes it was burning. “I think we can, sir,” answered Somers. Preble looked intently at the young man a moment and then inquired if he should have the time reduced, or the port-fire made shorter. “I ask for no port-fire at all, sir,” was the reply, firmly but quietly expressed.

After this interview, Somers expressed his determination not to allow himself to be captured. The commodore had felt it to be his duty to point out the great importance of not letting so large an amount of powder fall into the enemy’s hands, the Tripolitans being thought to be short of ammunition, and all the circumstances united had a tendency to increase the feeling of stern determination in the minds of the two officers who were to go in. Both were singularly quiet men in their ordinary habits, perfectly free from any thing like noisy declarations or empty boastings of what they intended to perform, and this simple announcement of their intentions not to be taken, appears to have made a deep and general impression among their brethren in arms.

On the afternoon of the 4th September, Somers prepared to take his final departure from the Nautilus, with a full determination to carry the ketch into Tripoli that night. Previously to quitting his own vessel, however, he fell that it would be proper to point out the desperate nature of the enterprise to the four men he had selected, that their services might be perfectly free and voluntary. He told them he wished no man to accompany him who would not prefer being blown up to being taken; that such was his own determination, and that he wished all who went with him to be of the same way of thinking. The boat’s crew gave three cheers in answer, and each man is said to have separately asked to be selected to apply the match. Once assured of the temper of his companions, Somers took leave of his officers, the boat’s crew doing the same, shaking hands and expressing their feelings as if they felt assured of their fates in advance. This was done in good faith, and yet cheerfully; and, of all the desperate service undertaken by that devoted squadron, none was ever entered on with so many forebodings of the fatal consequences to those concerned in it. Each of the four men made his will verbally; disposing of his effects among his shipmates like those who are about to die with disease.

It would seem that the Constitution’s boat did not join the ketch until it was dusk. When the two crews were mustered, it was found that Mr. Israel had managed to get out of the frigate and to join the party; whether by collusion, or not, it is now impossible to say. Finding him on board, and admiring his determination to make one of the party, Somers consented to his remaining. One account says he was sent by Preble with a final order, but it is hardly probable Somers would have allowed him to remain under such circumstances. He was more likely to be smuggled in by means of the cutter, and to be kept when there was no boat by which he could be sent back. The night of the 4th was not particularly dark, though it could scarcely be accounted clear. The stars were visible, but there was a haze on the water that rendered objects more uncertain than they would otherwise have been. In this respect the light was favorable enough, as the rocks could be seen, while the real character of the ketch would not be so likely to be discovered from the shore. The wind was light, from the eastward, but fair.