On 27 September 1851, Palmerston communicated the casus belli of Her Majesty’s Government against Dahomey and Lagos to the Admiralty. He began,
The watchful activity of Her Majesty’s cruizers, the multiplication of treaties with the native chiefs, and the operations last year at the Gallinas, appear to have nearly rooted out the Slave Trade from the coast north of the line. There remain, however two perserving offenders, the King of Dahomey and the Chief of Lagos, who still refuse to yield to persuasion, and who continue to thwart and to frustrate the measures of Her Majesty’s Government. Her Majesty’s Government cannot any longer permit that the accomplishment of a great purpose… be marred and defeated by the criminal and piratical resistance of two barbarous African chiefs.
Pertaining to Dahomey it declared a blockade of the coast, not to be “raised until the Chief of Dahomey shall have concluded and signed an agreement, by which he shall bind himself to give up totally and entirely the Slave Trade.” Moving on to Lagos, Palmerston writes,
The Chief of Lagos appears by all account to be a barbarous savage who has been put up and is supported by a set of slave-traders who have established themselves on the Island of Lagos…. Her Majesty’s Government have been informed… that there would be no great difficulty in sending into Lagos the small force which would be sufficient for the purpose of expelling the present chief and the slave traders by whom he is supported, and for re-establishing in his stead the former chief, Akitoye…. It is the Queen’s pleasure that the Commodore on the west coast of Africa… undertake it if it could be accomplished without much difficulty or risk.
It stated that the most “desirable result would be the expulsion of the present chief” Kosoko but allowed that any engagement made by Kosoko “would probably be observed only so long as he was strictly watched and forcibly prevented from breaking it.” A week later Palmerston reiterated that the objective was ending the foreign slave trade not necessarily the removal of a ruler, clarifying that if a “satisfactory arrangement shall have been made” with either chief prior to the execution of the Queen’s commands, they “shall be considered cancelled.”
Neither chief made satisfactory arrangements. The fifth Dahomean mission returned from Abomey empty handed and Beecroft’s long awaited negotiations with Kosoko collapsed on the first day. Kosoko, having suffered from suppression efforts and aware of Akitoye’s alliance with the British, curtly informed Beecroft “that he would not enter into any treaty with the English, and did not wish their friendship.” Beecroft retired to the British fleet sailing off the Lagosian coast and consulted with senior naval officers of the Bights Division. Together they determined that his February 1851 instructions justified coercive action. Five days later, on 25 November, “with the firm belief that… a simple demonstration of our power, [would] cause him to accede to our terms” Beecroft sailed towards Lagos at the head of four warships firing warning shots while flying a “most conspicuous white flag.” Already distrustful of British intentions Kosoko interpreted this act as an invasion. He rallied an army and returned fire with “five or six large guns and many swivels” forcing the British to withdraw after suffering two dead and ten wounded. Meanwhile, having received the Queen’s orders on 20 November 1851, Commodore Bruce made preparations for the blockade of Ouidah and sailed for Lagos, arriving there on 18 December. Upon learning of the first assault, he concluded, “the position of affairs now leaves but one course of action open to me, which is, to inflict a summary and retributive punishment upon the chiefs of Lagos.” Less than a month after the smoke cleared over Lagos, with “his line of coast… from the opening at Grand Popoe [sic] to Lagos” blockaded, King Gezo along with his principal chiefs and agents succumbed and signed a treaty prohibiting “any person within their jurisdiction, from selling or assisting in the sale of any slaves for transportation to a foreign country.”
 U.K., “Viscount Palmerston to the Lords Commissioners of the Admiralty,” 27 September 1851, PRRL, no. 43.
 U.K., “Mr. Addington to the Secretary of the Admiralty,” 8 October 1851, PRRL, no. 44.
 U.K., “Consul Beecroft to Viscount Palmerston,” 4 October 1851, PRRL, no.48; U.K., “The King of Dahomey to Her Majesty Queen Victoria,” 7 September 1851, PRRL, no. 48 en 2.
 U.K., “Consul Beecroft to Viscount Palmerston,” 26 November 1851, PRRL, no. 55; U.K., “Minute of a Conference with Kosoko, Chief of Lagos,” 20 November 1851, PRRL, no. 55 en 2.
 For Beecroft’s instructions see U.K., “Viscount Palmerston to Consul Beecroft,” 21 February 1851, PRRL, no. 25. For Beecroft’s deliberation with naval commanders on the scene see U.K., “Commander Heath to the Secretary of the Admiralty,” 17 December 1851, PRRL, no. 56 en. 1. Beecroft did not attack Lagos to protect the missionaries; he was “satisfied that Abbeokuta is safe from an attack” until the following spring (U.K., “Commodore Bruce to the Secretary of the Admiralty,” 1 November 1851, PRRL, no.61 en. 1).
 U.K., “Consul Beecroft to Viscount Palmerston,” 26 November 1851, PRRL, no. 55; U.K., “Commander Heath to the Secretary of the Admiralty,” 17 December 1851, PRRL, no. 56 en. 1; U.K., “Return of Force employed at the Expedition up Lagos River, on the 25th November, 1851,” PRRL, no.56 en. 2.
 U.K., “Commander Heath to the Secretary of the Admiralty,” 17 December 1851, PRRL, no 56 en. 1. When the British mission crossed into the lagoon for the 20 November diplomatic mission they “were met by messengers from Kosoko… begging them not to come up in force, as the inhabitants of the town were much excited.”
 U.K., “Commodore Bruce to the Secretary of the Admiralty,” 6 December 1851, PRRL, no. 62 en. 1; U.K., “Commodore Bruce to the Secretary of the Admiralty, 19 December 1851, PRRL, no. 65 en. 1.
F.O., “Correspondence,” BFSP, 1852-1853, 42: Class B, no.72 en. 2. For the text of the Dahomean treaty see F.O., “Treaties &c, between Great Britain and Native Chiefs and States on the West Coast of Africa, Relative to the Slave Trade,” BFSP, 1852-1853, 42: no. 2. The Dahomean treaty made no stipulation for the protection of Abeokuta and, unlike all other anti-slave trade treaties, it did not authorize Great Britain to act unilaterally in enforcing its provisions.