Jomini was born in Payerne in the canton of Vaud, Switzerland, on March 6, 1779, where his father served as mayor. The Jominis "were an old Swiss family" of Italian descent with a decidedly pro - French outlook. As a young boy, Jomini "was fascinated by soldiers and the art of war," and hoped to join the military, but his parents pushed him towards a career in business. As a result, Jomini entered a business school in Aarau at the age of 14.

In April 1795, Jomini left school and went to work at the banking house of Monsieurs Preiswerk in Basle. In 1796, he moved to Paris where he worked first at another banking house and then as a stock broker. After a short time in banking, however, "Jomini convinced himself that the tedious life of a banker was not to be compared with the life afforded in French Army," and decided to become a military officer as soon as he found an opportunity.

In 1798, after the establishment of the Helvetic Republic, Jomini became an "eager revolutionary", following the example of Frédéric - César de La Harpe and found a position in the new Swiss government as a secretary for the Minister of War with the rank of captain. In 1799, after being promoted to the rank of major, Jomini took responsibility for reorganizing the operations of the ministry. In that capacity, he standardized many procedures, and used his position "to experiment with organizational systems and strategies."

After the peace of Lunéville in 1801, Jomini returned to Paris, where he worked for a military equipment manufacturer. He found the job uninteresting, and spent most of his time preparing his first book on military theory: Traité des grandes operations militaires (Treatise on Grand Military Operations). Michel Ney, one of Napoleon's top generals, read the book in 1803 and subsidized its publication. The book appeared in several volumes from 1804 to 1810, and was "quickly translated and widely discussed" throughout Europe.

In 1805, Jomini served in the campaign of Austerlitz as a volunteer aide - de - camp on Ney's personal staff, and in December of that year, he was offered a commission as a colonel in the French Army. He joined without hesitation and served on Ney's staff. Jomini fought with Ney at the Battle of Ulm and served as his senior aide - de - camp at the Battle of Jena.

In 1806 Jomini published his views as to the conduct of the impending war with Prussia. This, along with his knowledge of Frederick the Great's campaigns, which Jomini had described in the Traité, led Napoleon to attach him to his own headquarters. Jomini was present with Napoleon at the Jena and at Eylau he won the cross of the Legion of Honour.

After the peace of Tilsit Jomini was made chief of the staff to Ney and created a Baron. In the Spanish campaign of 1808 his advice was often of the highest value to the marshal, but Jomini quarreled with his chief, and was left almost at the mercy of his numerous enemies, especially Louis Alexandre Berthier, the emperor's chief of staff.

Overtures had been made to him, as early as 1807, to enter the Russian service, but Napoleon, hearing of his intention to leave the French army, compelled him to remain in the service with the rank of general of brigade.

For some years thereafter Jomini held both a French and a Russian commission, with the consent of both sovereigns. But when war between France and Russia broke out, he was in a difficult position, which he dealt with by taking a non - combat command on the line of communication.

Jomini was thus engaged when the retreat from Moscow and the uprising of Prussia transferred the seat of war to central Germany. He promptly rejoined Ney, took part in the Battle of Lützen. As chief of the staff of Ney's group of corps, he rendered distinguished services before and at the Battle of Bautzen, and was recommended for the rank of general of division. Berthier, however, not only erased Jomini's name from the list but put him under arrest and censured him in army orders for failing to supply certain staff reports that had been called for.

How far Jomini was responsible for certain misunderstandings which prevented the attainment of all the results hoped for from Ney's attack at Bautzen, we cannot be sure. But the pretext for censure was in Jomini's own view trivial and baseless, and during the armistice Jomini did as he had intended to do in 1809 – 1810, and went into the Russian service. As things then were, this was tantamount to deserting to the enemy, and so it was regarded by many in the French army, and by not a few of his new comrades. It must be observed, in Jomini's defense, that he had for years held a dormant commission in the Russian army and that he had declined to take part in the invasion of Russia in 1812. More important — and a point that Napoleon commented upon — was the fact that he was a Swiss citizen, not a Frenchman.

His Swiss patriotism was indeed strong, and he withdrew from the Allied Army in 1814 when he found that he could not prevent the allies' violation of Swiss neutrality. Apart from love of his own country, the desire to study, to teach and to practice the art of war was his ruling motive. At the critical moment of the battle of Eylau he had exclaimed, "If I were the Russian commander for two hours!" On joining the allies he received the rank of lieutenant - general and the appointment of aide - de - camp from the tsar, and rendered important assistance during the German campaign: an accusation that he had betrayed the numbers, positions and intentions of the French to the enemy was later acknowledged by Napoleon to be without foundation. As a Swiss patriot and as a French officer, he declined to take part in the passage of the Rhine at Basel and the subsequent invasion of France.

In 1815 he was with Tsar Alexander in Paris, and attempted in vain to save the life of his old commander Ney. This defense of Ney almost cost Jomini his position in the Russian service. He succeeded, however, in overcoming the resistance of his enemies and took part in the Congress of Vienna.

After several years of retirement and literary work, Jomini resumed his post in the Russian army, and in about 1823 was made a full General. Thenceforward until his retirement in 1829 he was principally employed in the military education of the Tsarevich Nicholas (afterwards Emperor) and in the organization of the Russian staff college, which was opened in 1832 and bore its original name of the Nicholas Academy up to the October Revolution of 1917. In 1828 he was employed in the field in the Russo - Turkish War, and at the Siege of Varna he was awarded the Grand Cordon of the Alexander Order.

This was his last active service. In 1829 he settled in Brussels which served as his main place of residence for the next thirty years. In 1853, after trying without success to bring about a political understanding between France and Russia, Jomini was called to St Petersburg to act as a military adviser to the Tsar during the Crimean War. He returned to Brussels upon the conclusion of peace in 1856. Later he settled at Passy near Paris. He was busily employed up to the end of his life in writing treatises, pamphlets and open letters on subjects of military art and history. In 1859 he was asked by Napoleon III to furnish a plan of campaign for the Italian War. One of his last essays dealt with the Austro - Prussian War of 1866 and the influence of the breech - loading rifle. He died at Passy only a year before the Franco - Prussian War of 1870 - 71.

Jomini's military writings are frequently caricatured: he took a didactic, prescriptive approach, reflected in a detailed vocabulary of geometric terms such as bases, strategic lines, and key points. His operational prescription was fundamentally simple: put superior combat power at the decisive point. In the famous theoretical Chapter 25 of the Traité de grande tactique, he stressed the exclusive superiority of interior lines.

As one writer rather partial to Carl von Clausewitz – Jomini's great competitor in the field of military theory – put it:

Jomini was no fool, however. His intelligence, facile pen, and actual experience of war made his writings a great deal more credible and useful than so brief a description can imply. Once he left Napoleon's service, he maintained himself and his reputation primarily through prose. His writing style -- unlike Clausewitz's -- reflected his constant search for an audience. He dealt at length with a number of practical subjects (logistics, seapower) that Clausewitz had largely ignored. Elements of his discussion (his remarks on Great Britain and seapower, for instance, and his sycophantic treatment of Austria's Archduke Charles) are clearly aimed at protecting his political position or expanding his readership. And, one might add, at minimizing Clausewitz's, for he clearly perceived the Prussian writer as his chief competitor. For Jomini, Clausewitz's death thirty - eight years prior to his own came as a piece of rare good fortune.

Jomini took the view that the amount of force deployed should be kept to the minimum in order to lower casualties and that war was a science, not an art. While in Russian service, Jomini tried hard to promote a more scientific approach at the general staff academy he helped to found. Prior to the American Civil War, the translated writings of Jomini were the only works on military strategy that were taught at the United States Military Academy at West Point. The regular army officers who became the general officers for both the Union and the Confederacy in that conflict began by following Jominian principles, but soon found that the peculiarities of American geography, particularly in the west, forced them to move beyond his geometric conventions and find other strategic solutions to the problems which confronted them.