I'll quote an old soc.history.what-if post of mine:
**
During the 1850s there was a marked resurgence of slave trading into Cuba,
and there is no doubt that much of it was carried out by American ships
under the protection of the American flag. British enforcement of the ban
on the African slave trade, which had slackened somewhat during the
Crimean War, returned to a higher level in 1857 just as James Buchanan was
taking office as president, and installing Lewis Cass, who had a
reputation as an Anglophobe, as Secretary of State...
With Palmerston as Prime Minister in Britain and Cass as
Secretary of State in the US, one might expect some tense moments in
Anglo-American relations, and one would not be mistaken. (Apart from the
"right of visit" controversy, another source of tension was Central
America and divergent US and British interpretations of the Clayton-Bulwer
treaty. I will discuss that in another post.)
As British boardings of American vessels along the African coast became
more frequent, the Foreign Office intensified pressure on the US
government. In a note written December 24, 1857, Lord Napier, the British
minister in Washington, presented evidence of American involvement in the
illegal Cuban trade (more than twenty ships proven or strongly suspected
to be slavers) and argued that the trade could be wiped out if only the US
would meet its obligations under the Webster-Ashburton treaty of 1842 and
join Britain in a vigorous naval effort at suppression.
Cass's reply came three and a half months later. Besides complaining
about British naval excesses, he declared that the "joint blockade" of the
African coast had proven ineffective and suggested that other means be
tried. One was to shift emphasis across the Atlantic: instead of trying
to prevent the exports of slaves from Africa, he advised, let Britain
induce Spain to "shut the ports of Cuba to their entrance." Such a change
in strategy had in fact been considered in Britain for some time, and was
just then being put into effect by London--though by far more militant
means than Cass had in mind or could accept. British naval forces
"imposed a virtual blockade of Cuba, detaining and searching vessels of
all nations for evidence of slave trading and often firing shots at those
that sought to escape inspection. The New York Times of May 27 listed
twenty-eight acts of aggression against American ships, including
harassment within Cuban ports as well as at sea. Even some domestic
coasting vessels were caught in the British net." Don E. Fehrenbacher,
*The Slaveholding Republic: An Account of the United States Government's
Relations to Slavery* (Oxford UP 2001), p. 184
A storm of protest erupted throughout the country. Buchanan dispatched
warships to the Gulf of Mexico with orders to "protect all vessels of the
United States on the high seas from search or detention by the vessels of
war of any other nation." In Congress, which had just concluded a long and
bitter struggle over the Lecompton Constitution for Kansas, there was
remarkable unity among pro-Lecompton Democrats, anti-Lecompton Democrats,
Whigs/Americans, and Republicans in denouncing the British "outrages." As
Fehrenbacher (p. 185) notes:
"If authorized, said [Republican] Anson Burlingame of Massachusetts, those
offenses were acts of war; if not, they amounted to robbery at sea and
should be dealt with accordingly. Stephen A. Douglas of Illinois and
Robert Toombs of Georgia urged the seizure of British warships in
retaliation. Even Gamaliel Bailey's vehemently antislavery *National Era*
rallied to the support of the Buchanan administration, declaring that the
United States must 'resist to the death the insolent assumption of any
foreign power to subject our ships to detention and examination.'"
Why has this crisis, which seemed so dangerous at the time, been so
forgotten? Probably because it only lasted a few weeks and was already
subsiding when Congress adjourned on June 14. Leaders of Britain's new
Conservative government headed by Lord Derby, which had supplanted the
Palmerston government in February, had no desire to aggravate a crisis not
of their making. They hastened to rein in the West Indian Fleet and
disavow its aggressive conduct, but not without stumbling into another
round of the perennial Anglo-American argument on the subject of visit and
search.
Napier, in his Christmas Eve note, had argued that display of the American
flag, although it exempted a slaver from *search* did not protect it from
*visit*. Lord Derby's Foreign Secretary, Lord Malmesbury, later spoke in
similar terms, thus apparently reasserting a right that Aberdeen had
ostensibly renounced in the early 1840s--that is, the right to board any
vessel for the limited purpose of verifying its nationality.
(Some background on this dispute: Britain had claimed a right to board
merchant vessels suspected of illegally carrying the US flag. The US
acknowledged that it had no ground for protest when such suspicions proved
accurate. The issue was what happened when there was *mistaken* suspicion,
and the vessel boarded turned out to be a bona fide American vessel. In
December, 1841 Aberdeen virtually conceded that such mistakes constituted
trespass: "If, in spite of the utmost caution, an error should be
committed, and an American vessel should suffer loss and injury, it would
be followed by prompt and ample reparation." Ultimately Britain did pay
indemnity for some of its pre-1842 seizures. Despite this, the issue of
right of visitation had not been *formally* resolved; British naval
commanders continued to operate under virtually the same instructions they
had before the Webster-Ashburton Treaty, and though visits were uncommon
between 1842 and 1857, they did occur. Furthermore, since a ship flying
false colors was also likely to carry false papers, suspicious officers
sometimes turned a "visit" into a "search." But during this period,
complaints about British conduct were generally lodged and parried by
naval commanders on station, rather than by diplomats in Washington and
London.)
Cass's reply to Napier restated the American position forcefully, but in a
way that reflected the moderating hand of Buchanan, who was determined to
conduct his own foreign policy (after all, Buchanan had more foreign
policy experience than any president since John Quincy Adams). After
insisting once again that there was no right of visit or search in
peacetime under international law, Cass acknowledged that a vessel falsely
assuming an American character had no claim to American protection.
Whoever investigated such a vessel, however, did so at his own risk:
"As the identity of a person must be determined by the officer bearing a
process for his arrest, and determined at the risk of such officer, so
must the national identity of a vessel be determined, at a like hazard to
him who, doubting the flag she displays, searches her to ascertain her
true character. There, no doubt, may be circumstances which would go far
to modify the complaints a nation would have a right to make for such a
violation of its sovereignty. If the boarding officer had just grounds for
suspicion, and deported himself with propriety in the performance of his
task, doing no injury and peaceably retiring when satisfied of his error,
no nation would make such an act the subject of serious reclamation."
As late as June 8, Malmesbury appeared unwilling to give up the right of
visit, but then, after having consulted the law officers of the Crown, he
suddenly reversed himself and declared: "Her Majesty's government
recognize the principles of international law as laid down by General Cass
in his note of the 10th of April." This statement, together with the
curbing of Britain's Cuban squadron, resolved the crisis in a way that
left Americans feeling triumphant. At a banquet in London on the Fourth of
July the 150 celebrants all rose to their feet and cheered lustily when
the American minister, George M. Dallas, announced that the long
controversy was "finally ended." The Times of London, addressing an
editorial to the American nation a few days later, grudgingly
acknowledged: "You have now, it appears, got finally rid of that remnant
of your tutelage, the right of visit."
Whether the resolution of the crisis was quite the American triumph and
British surrender portrayed by Buchanan and Cass (and most American
historians) may be doubted. Britain in effect simply went back to the
1842-57 status quo. One can even argue that the US made the more
significant concession by acknowledging that *reasonable* (even if
erroneous) suspicion of misuse of the US flag could mitigate damages.
Britain continued to board ships suspected of such misuse, but because the
number of such incidents decreased, and because they were off the coast of
Africa rather than in the Caribbean, tensions on the issue never reverted
to their 1858 level, even after Palmerston returned to office in 1859.
But of course by then the retreat from the 1857-8 tactics was a *fait
accompli.* The real question is: what if Palmerston had still been in
office in mid-1858 and had refused to yield on either the right of visit
in general or the aggressive tactics of the West India Fleet in
particular? Could this have resulted in a British-American war?
(BTW, one thing that must be said in all fairness to Buchanan, not
otherwise one of my favorite presidents: he did realize that the US
position--rejecting any system of international police abridging freedom
of the seas--morally required the US to do more on its own initiative
against the slave trade. Secretary of the Navy Toucey added four steamers
to the African squadron--and moved their base from the Cape Verde Islands
to a point on the African mainland much nearer to the center of slave-
trade activity--and also reinforced naval forces in the Gulf of Mexico to
guard the approaches to Cuba. American warships, which averaged only one
prize per year from 1851 through 1858, seized five slavers in 1859 and
fifteen in 1860. Of those twenty captures, twelve were made on the
African coast and eight in Cuban waters. Unfortunately, this made only a
slight dent in the slave trade to Cuba. Nevertheless, inadequate as
Buchanan's effort was, it was still the strongest attack on the slave
trade any US administration had undertaken.)
https://groups.google.com/d/msg/soc.history.what-if/_yoKr_60DrA/Ae-nZDkEixoJ