Sir Henry Sidney became his mentor, and he was educated at Eton and Oxford University, where he learned to speak French and Spanish and studied the arts of war and navigation. He went on to reside at the Inns of Chancery in London c.1560–1561.
Quid non? ("Why not?") and Mutare vel timere sperno ("I scorn to change or to fear"), indicates how he chose to live his life. He was present at the siege of Newhaven in Havre-de-grâce (le Havre), Normandy, where he was wounded in June 1563. By July 1566 he was serving in Ireland under the command of Sidney (then Lord Deputy) against Shane O'Neill, but was sent to England later in the year with dispatches for the Queen. (See Plantations of Ireland and Tudor conquest of Ireland). At that point he took the opportunity of presenting the Queen with his A discourse of a discoverie for a new Passage to Cataia (published in revised form in 1576), treating of the exploration of a Northwest Passage by America to Asia. Within the year he had set down an account of his strange and turbulent visions, in which he received the homage of Solomon and Job, with their promise to grant him access to secret mystical knowledge.
Gilbert returned to Ireland and, after the assassination of O'Neill in 1569, he was appointed to the profitless office of governor of Ulster and served as a member of the Irish parliament. At about this time he petitioned the Queen's principal secretary, Lord Burghley, for a recall to England - "for the recovery of my eyes" - but his ambitions still rested in Ireland, and particularly in the southern province of Munster. In April 1569 he proposed the establishment of a presidency and council for the province, and pursued the notion of an extensive settlement around Baltimore (in modern County Cork), which was approved by the Dublin council. At the same time he was involved with Sidney and the secretary of state, Sir Thomas Smith, in planning a large settlement of the northern province of Ulster by Devonshire gentlemen.
Gilbert's actions in the south of Ireland played a significant part in the outbreak of the first of the Desmond Rebellions. A kinsman of his, Sir Peter Carew (another Devonshire man), was pursuing a provocative, and somewhat far-fetched, claim to the inheritance of certain lands within the Butler territories in south Leinster. The Earl of Ormond - a bosom companion of the Queen's from her troubled youth and head of that family - was absent in England, and the clash of his family's influence with the lawful authority of Carew's claim created havoc.
Gilbert was eager to participate and, after Carew's seizure of the barony of Idrone (in modern County Carlow), he pushed westward with his forces across the river Blackwater in the summer of 1569 and joined up with his kinsman to defeat Sir Edmund Butler, a younger brother of the Earl's. Violence spread in a confusion from Leinster and across the province of Munster, when the Geraldines of Desmond went into rebellion. Gilbert was then created colonel by Lord Deputy Sidney and charged with the pursuit of the rebel James Fitzmaurice Fitzgerald (whom Gilbert considered, "a silly wood-kerne").
The Geraldines were driven out of Kilmallock, but returned to lay siege to Gilbert, who drove off their superior force in a sally, during which his horse was shot from under him and his buckler transfixed with a spear. After that initial success, he showed courage in striking out into rebel territory, and managed to march unopposed through Kerry and Connello, taking 30-40 castles without the aid of artillery.
During the three weeks of this campaign, all enemies were treated without quarter and put to the sword - including women and children - which explains, perhaps, the swiftness with which so many castles had been abandoned before Gilbert's aggression. He is also said to have sent Captain Apsley into Kerry to inspire terror.
Gilbert's attitude to the Irish may be captured in one quote from him, dated 13 November 1569: "These people are headstrong and if they feel the curb loosed but one link they will with bit in the teeth in one month run further out of the career of good order than they will be brought back in three months." In order to cow local supporters of the rebels, he chose to put on gruesome spectacles: after a day's killing he would order the decapitation of the scattered corpses so that the heads could be brought to his camp in the evening, where they were arranged in two parallel rows, making a pathway to the flaps of his tent, along which the supplicants would tread in the presence of their late fathers, brothers and sons. John Perrot also used the practice at Kilmallock a few years later).
In time, Ormond returned from England and called in his brothers, which caused the Geraldine resistance to weaken. In December 1569, after one of the chief rebels had come in to the government and confessed his treason, Gilbert received his knighthood at the hands of Sidney in the ruined Fitzmaurice camp, reputedly amid heaps of slain gallowglass warriors. Fitzmaurice stayed out in rebellion (only coming in to submit in 1573), and one month after Gilbert's return to England he retook Kilmallock with 120 foot, defeating the garrison and sacking the town for three days, leaving it "the abode of wolves".
In 1570 Gilbert returned to England, where he married Anne Aucher, who was to bear him six sons and one daughter. However, it has been conjectured - following Smith's observation that the only way to soothe Gilbert's temper was to send a boy to him - that he was an "intermittent homosexual", or perhaps a pederast.
Gilbert was elected to parliament as a member for Plymouth, and controversially argued for the crown prerogative in the matter of royal licences for purveyance. In business affairs, he involved himself in an alchemical project with Smith, whereby iron was to be transmuted into copper and antimony, and lead into mercury.
By 1572 Gilbert had turned his attention to the Netherlands, where he fought an unsuccessful campaign in support of the Dutch Sea beggars at the head of a force of 1500 men, many of whom had deserted from Smith's aborted plantation in the Ards of Ulster. In the period 1572–1578 Gilbert settled down and devoted himself to writing. In 1573 he presented Elizabeth I with a proposal for an academy in London, which was eventually put into effect by Sir Thomas Gresham upon the establishment of Gresham College. Gilbert also helped to set up the Society of the New Art with Lord Burghley and Robert Dudley, Earl of Leicester, both of whom maintained an alchemical laboratory in Limehouse.
Thereafter, Gilbert's life was spent in a series of failed ship expeditions, the financing of which exhausted his own fortune and a great part of his family's. He backed Martin Frobisher's trip to Greenland, which yielded a cargo of a mysterious yellow rock, subsequently found to be worthless. In pursuit of one of his own projects, he sailed from Plymouth for America in November 1578 with 7 vessels in his fleet, which was scattered by storms and forced back to port some 6 months later; the only vessel to have penetrated the Atlantic to any great distance was the Falcon under Raleigh's command.
In pursuit of his Irish commission, Gilbert set sail in June 1579 after a spell of bad weather, and promptly got lost in fog and heavy rains off Land's End, an incident that caused the Queen thereafter to doubt his seafaring abilities. His fleet was then driven into the Bay of Biscay, and the Spanish soon sailed into Dingle harbour, where they made their rendez-vous with the rebels. In October he managed to put into the port of Cobh in Munster, where he delivered a terrible beating to a local gentleman, smashing him about the head with a sword. He then fell into a row with a local merchant, whom he slew on the dockside.
Gilbert was one of the leading advocates for a north-west passage to the land of Cathay (present-day China), noted in great detail for its abundance of riches by Marco Polo in the 13th century. Gilbert made an elaborate case to counter the calls for a north-eastern route. During the winter of 1566 Gilbert and his principal antagonist Anthony Jenkinson (who had sailed to Russia and crossed the country down to the Caspian Sea), argued the pivotal question of polar routes before Queen Elizabeth. Gilbert claimed that any north-east passage was far too dangerous; "the air is so darkened with continual mists and fogs so near the pole that no man can well see either to guide his ship or direct his course." By logic and reason a north-west passage must exist announced Gilbert. Columbus had discovered America with far less evidence to go on. It was imperative for England to catch up, settle in new lands and thus challenge the Iberian powers. Gilberts contentions won support and money was raised, chiefly by the London merchant Michael Lok, for an expedition. The fearless Martin Frobisher was appointed captain and left England in June 1576. Frobisher's search for a north-west passage proved fruitless. He returned with black stone and an inuit.
The six year exploration licence Gilbert had secured by letters patent from the crown in 1578 was on the point of expiring, when he succeeded in 1583 in raising significant sums from English Catholic investors. The investors were constrained by penal laws against recusants in their own country, and loathe to go into exile in hostile parts of Europe; thus, the prospect of an American adventure appealed to them, especially when Gilbert was proposing to seize some 9 million acres (36,000 km²) around the river Norumbega, to be parcelled out under his authority (although to be held ultimately of the crown).
The Catholic investment didn't work out - partly because of the privy council's insistence that the investors pay their recusancy fines before departing, partly because of efforts by Catholic clergy and Spanish agents to dissuade their interference in America - but Gilbert did manage to set sail with a small fleet of 5 vessels in June 1583. One of the vessels - the Bark Raleigh, owned and commanded by Raleigh himself - had to turn back owing to lack of victuals. Gilbert's crews were made up of misfits, criminals and pirates, but in spite of the many problems caused by their lawlessness, the fleet did manage to reach Newfoundland.
On arriving at the port of St. John's, Gilbert found himself temporarily blockaded by the fishing fleet under the organisation of the port admiral (an Englishman) on account of piracy committed against a Portuguese vessel in 1582 by one of Gilbert's commanders. Once this resistance was overcome, Gilbert waved his letters patent about and, in a formal ceremony, took possession of Newfoundland (including the lands 200 leagues to the north and south) for the English crown on 5 August 1583. This involved the cutting of turf to symbolize the transfer of possession of the soil, according to the common law of England. He claimed authority over the fish stations at St. John's and proceeded to levy a tax on the fisherman from several countries who worked this popular area near the Grand Banks.
Within weeks his fleet departed, having made no attempt to form a settlement, due to lack of supplies. During the return voyage, Gilbert insisted on sailing in his hardy old favourite, the Squirrel. He soon ordered a controversial change of course for the fleet, and owing to his obstinacy and disregard of the views of superior mariners one of the vessels ran aground with some loss of life (probably on the western shoals of Sable Island). Later in the voyage a sea monster was sighted, said to have resembled a lion with glaring eyes.
After discussions with Edward Hayes and William Cox, captain and master of the Golden Hind, Gilbert had decided on 31 August to return. The wind was in their favor as they sped back to Cape Race in two days and were soon clear of land. Gilbert had injured his foot on the frigate Squirrel and, on 2 September, came aboard the Golden Hind to have his foot bandaged and to discuss means of keeping the two little ships together on the voyage. Gilbert refused to leave the Squirrel, while the vessels continued on the Atlantic crossing. After a strong storm, they had a spell of clear weather and made fair progress: Gilbert came aboard the Golden Hind again, visited with Hayes, and insisted once more on returning back to the frigate Squirrel, even though Hayes insisted she was over-gunned and unsafe for sailing. Nearly 900 miles away from Cape Race, they encountered high waves of heavy seas, "breaking short and high Pyramid wise", said Hayes.
On 9 September, the frigate Squirrel was nearly overwhelmed but recovered. Despite the persuasions of others, who wished him to take to one of the larger vessels, Gilbert stayed put and was observed sitting in the stern of his little frigate, reading a book. When the Golden Hind came within hailing distance, the crew heard him cry out repeatedly, "We are as near to Heaven by sea as by land!" as he lifted his palm to the skies to illustrate his point. At midnight the frigate's lights were extinguished, and the watch on the Golden Hind cried out that, "the Generall was cast away". The Squirrel had gone down with all hands.
It is thought Gilbert's reading material was the Utopia of Sir Thomas More, which contains the following passage: "He that hathe no grave is covered with the skye: and, the way to heaven out of all places is of like length and distance."
Gilbert was part of a remarkable generation of Devonshire men, who combined the roles of adventurer, writer, soldier and mariner - often in ways as equally loathsome as admirable. He was outstanding for his initiative and originality, if not for his successes, but it is in his efforts at colonization that he had most influence. Ireland ended up as a brutal disaster (although Ulster and Munster were in time colonized), but the American adventure did eventually flourish. The formality of his annexation of Newfoundland eventually achieved reality in 1610; but perhaps of more significance was the reissue to Raleigh in 1584 of Gilbert's patent, on the back of which he undertook the Roanoke expeditions, the first sustained attempt by the English crown to establish colonies in North America.