The initial exploitation of the timber and raw materials of Madeira, the Azores, the Canary Islands, and the Cape Verde Islands had ended, and it rapidly became clear that the most profitable use of the new territories would be sugar production.

The labor involved is heavy, and Europeans refuse to work as more than supervisors.

The solution has been to bring in slaves from Africa.

The first enslaved Africans brought to Portugal had arrived in 1441 from northern Mauritania, the fruits of the expedition commanded by Lançarote de Freitas.

The maritime town of Lagos is the first slave market created in Portugal for the sale of the two hundred and thirty-five enslaved Berbers—the Mercado de Escravos, which opens in 1444.

The regent prince Peter of Coimbra had in 1443 granted his brother Henry the Navigator an exclusive monopoly on all trade south of Cape Bojador.

A consortium of merchants of Lagos, sometimes referred to as the Companhia de Lagos ('Lagos Company', although it was probably little more than a temporary association of merchants, rather than an incorporated company in the proper sense), have applied to Henry for a license.

Sometime in the 1430s or early 1440s, Henry had appointed one Lançarote de Freitas (better known simply as Lançarote de Lagos), trained as a squire and chamberlain in his household, as almoxarife (customs-collector) of Lagos.

Possibly on account of his intimate relationship with Henry, the Lagos merchants elect Lançarote as their head.

Having acquired their license, the Lagos company have equipped a fleet of six ships and about thirty men that had set out for the Arguin banks in the Spring of 1444.

Lançarote's fleet heads straight to the southern end of the Arguin Bay, where they had been told by Nuno Tristão's captives that populous fishing settlements could be found.

A pre-dawn raid on Nar (Nair island) yields the first set of captives.

This is followed up by raids on the larger neighboring island of Tider (Tidra island) and Cerina (Serenni peninsula).

In just a few days, the Lagos fleet takes captive some two hundred and thirty-five hapless Berber natives.

The remaining population having fled the coastal settlements and hidden in the hinterlands, there is little point remaining in the area.

By August, the fleet has arrived back in Lagos with their human cargo.

The spectacle of the disembarkation, partition and sale of the Arguin slaves in Lagos, in the presence of Prince Henry, mounted on his horse, is described in heartbreaking detail in Zurara's Crónica.

For this lucrative enterprise, Lançarote is knighted by Henry on the spot (even though, according to Zurara, Henry gave away his own allotment —some forty-six slaves, to which he was entitled as licenser of the expedition—among his captains and household servants).

Lançarote's squadron soon arrives at Barbary Point, the mouth of the Senegal River, which is as yet unexplored.

He dispatches Estêvão Afonso on a launch to search upriver for settlements.

The exploration doesn't get very far.

Venturing ashore at one point along the river bank, Afonso abducts two Wolof children from a local woodsman's hut, only to be chased down and furiously beaten by their father.

Having barely escaped with their lives, the launch immediately returns to the waiting caravels.

After sending back yet another caravel to Lagos, Lançarote proceeds with his five remaining ships around Cape Vert into Dakar Bay.

The squadron lands in the island of Bezeguiche (Gorée island), where they find a marker left behind by Álvaro Fernandes, a Portuguese explorer from Madeira who had preceded them there only a few weeks earlier.

Fernandes had attempted to take a few Wolof canoes captive, with the result that the Wolof tribesmen of the mainland are already alert and in arms against the arriving ships.

Not quite realizing this, Lançarote sends out Gomes Pires on a launch to the mainland to open contact with the local Wolof chieftains, but Pires's approach is prevented by a hail of arrows.

His first strategy foiled, Lançarote orders the Portuguese to prepare a raid on the mainland Wolof villages 'in the style of Arguin', but this comes to nothing.

Before being able to organize the attack, a sudden storm envelops the area, and forced the Portuguese caravels out of Bezeguiche bay, scattering them in various directions.

Lançarote manages to hold two other caravels (Álvaro de Freitas and Vicente Dias) together with him, but loses sight of the other two.

Realizing they are now too few to launch an attack on the Wolof mainland, Lançarote's trio sets sail back to the Arguin banks, where …

Lançarote's second Lagos fleet is just one of several that set out from Portugal for the Arguin banks in August, 1445 (or 1446).

Caught by bad weather, Lançarote arrives at Cape Blanc with only nine ships still together, the remaining having strayed off.

He proceeds to the northern end of the Arguin banks, anchoring in at ilha das Graças (possibly Madeleine island or Pelicans island).

There, Lançarote was met by one of his missing ships, Vicente Dias, who had gone on ahead to Arguin island and stumbled across a small fleet of three Lisbon ships, headed by Dinis Eanes de Grã, who had preceded them and devastated the remaining settlements on the northern end of the bay, taking some one hundred captives.

At Grã's suggestion, Lançarote's fleet, now thirteen strong (only Palançano's fusta remains unaccounted for) attacks Arguin island again, taking four captives, then heads to the southern end of Arguin Bay, taking fifty-seven captives at Tider and an additional five somewhere further down (possibly around Cape Timris).

The element of surprise being gone and the bulk of the population having already evacuated the coast, Lançarote's captives are principally Sanhaja Berber tribesmen who had decided to stay and put up a fight.

Dissatisfied with the meager number of captives and realizing that Arguin Bay is too thoroughly deserted to yield up any more, Lançarote decides to take his fleet south to raid the Wolof lands of Senegal, which had been discovered (but not yet raided) by Nuno Tristão and Dinis Dias the previous year.

However, not all his ships are up for the journey, several of them running short on supplies.

As a result, Lançarote partitions his fleet, taking only six or seven caravels with him, sending the remaining ships back to Lagos under the command of Soeiro da Costa (a few of which will conduct an unauthorized slave raid on the Canary islands of La Palma and Gomera on their way home).

…they anchor at Tider and take an additional fifty-nine captives, before returning to Lagos.

The remaining two ships (Lourenço Dias and Gomes Pires) make their way back to Portugal by themselves (Pires making a brief stop in Cape Blanc, to buy some seal pelts and slaves from some Berber traders).

Little more is heard about Lançarote de Lagos.

In number of captives, the 1445/6 slaving expedition had been somewhat of a disappointment (at least relative to the first 1444 expedition).

The prospect for future slave raids seems dim.

The Arguin banks are devastated and it is unlikely the Berber populations will return to the coasts in significant numbers, or allow themselves to be taken by surprise.

The Wolof-dominated coasts of Senegal are too strong and alert for small groups of venturing Portuguese slave-raiders.

If slave raids are to have any prospect of success, the element of surprise is necessary, which now means sailing well below Senegal to new 'hunting grounds' - lengthier expeditions which require probably more supplies and capital than what Lagos merchants are willing to front or captains willing to sail.

The killing of Nuno Tristão and his crew the next year (1446 or 1447) probably dampens any remaining enthusiasm among Lagos merchants for renewing the slave raids.