When the British surrendered at Yorktown on 19 October 1781, there were sixty battalions of infantry in the Continental establishment. Afterwards, as time passed and it appeared that the British intended no new attack, that number was steadily reduced. Finally, in November 1783, after a peace had been formally ratified, only one foot regiment remained, commanded by Henry Jackson. Then, on 2 June 1784, the end came even for that unit, leaving as the only authorized vestige of the Continental Army still in service fewer than a hundred men to guard military stores at West Point and at Fort Pitt.

Congress nevertheless realized the need for at least enough infantry to replace Jackson's regiment. Accordingly, the day after the latter was directed to be discharged, the legislators established a regiment which was to be raised and officered by obtaining volunteers from the militia of four of the states. This nonRegular unit, called the First American Regiment and commanded until 1 January 1792 by Josiah Harmar of Pennsylvania, gradually turned into a Regular outfit. It became known as the 1st Infantry in 1791, and in 1815 was redesignated as the 3d Infantry. From 1784 to 1787 Harmar's regiment was a hybrid, containing eight companies of infantry and two of artillery.
Although England was a constant threat to the new nation after the War for Independence, the Indians presented the most immediate menace. Accordingly, the First American Regiment was stationed on the frontier. In October 1790, the Miami Indians and their allies defeated the first field army, commanded by Harmar, to be organized by the government of the United States acting under the Constitution. This defeat caused the raising of another regiment of infantry in 1791, and the numbering of the old one as the 1st and the new one as the 2d. As a result of the radical reorganization after the War of 1812, the latter became the 1st Infantry.

Serious trouble with the Indians of the Northwest continued; indeed, in the very year the 2d Infantry was organized, the Miamis defeated the second force sent by the Federal government against them. The army defeated in 1791, led by Arthur St. Clair, consisted of the Regular establishment augmented by militia and a new species of foot troops known as levies. Goaded by defeats, Congress gradually increased the military establishment from 700 men in 1784 to 5,104 in 1793. As the size of the entire Army increased, so did the strength of the infantry elements. Regiments rose from 560 to 1,140 enlisted men, companies from 70 to 95. Regiment and battalion remained one and the same.

Two beatings inflicted by the Northwest Indians brought about an experiment in organization which had precedents in certain European corps and in some of the Continental Army. The entire military establishment was converted in 1792 into a legion, that is, into a field army in which the three combat branches, infantry, cavalry, and artillery, were combined in the same organization. The legion consisted of four sublegions. Each sub-legion contained infantry, riflemen, cavalry, and artillery; indeed it was the forerunner of the twentieth century regimental combat team.

Although Congress had authorized a total of five regiments on 5 March 1792, when the Legion of the United States came into being, none but the 1st and 2d Infantry were actually organized. Hence it was necessary to go out and recruit infantry for the 3d and 4th Sub-Legions. Likewise it was necessary to recruit the rifle units for all the sub-legions.

Command of the new Legion fell to Anthony Wayne, who had been a successful leader of light troops during the Revolution. Wayne did not employ the sublegions as such to any important extent; on the contrary, he combined the infantry from all of them, likewise the artillery, and so forth. However, he instituted so stern a system of discipline that he forged an army which, in 1794, finally beat the Indians of the Northwest and defied the power of England which had fostered Indian unrest.

Once the threat in that quarter was reduced, the need to hold a field army together seemed to diminish. What was needed instead, statesmen believed, was an organization which could easily be split up and parcelled out to guard the frontiers and the seacoast. As long as Henry Knox remained Secretary of War, the legionary form had a stout champion, but he left office at the end of 1794. The Legion persisted for another year and a half, then went out of existence by act of Congress effective 31 October 1796. In the new establishment the infantry of the four sublegions became the 1st, 2d, 3d, and 4th Infantry.

Peace promised to prevail, so that during 1796 and 1797 the entire Army was reduced, and the size of regiments and companies as well. For scattered use, a large complement of officers and small companies filled the bill.

All too soon the sense of security evaporated as war loomed with France. In consequence, the establishment swelled precipitately, and the strength of units with it. By 1799 a total of forty infantry regiments was authorized, although none but the 1st through the 4th ever attained the required strength. Only 3,400 men were raised for the 5th through the 16th, and none at all for any others. Fortunately, the war with France never took shape; by 1800 the crisis was over and the immediate need for more infantry gone. In addition, a new administration took office in 1801, an administration that almost pathologically feared a standing army. Accordingly, under Thomas Jefferson the infantry was cut back in 1802 to two regiments, the 1st and 2d.
Jefferson's administration had only a brief chance to test its convictions regarding a strong militia and a small standing army, for war clouds were gathering once more. The United States almost began the second war with England when the British warship Leopard attacked the American Chesapeake in 1807. This aggression caused Congress to add five Regular infantry regiments in 1808, the 3d through the 7th, and also to constitute the Regiment of Riflemen. The latter was a product of the Revolutionary experience and the first rifle unit since the end of the Legion in 1796. Rifle elements re-entered the service through the agency of Brig. Gen. James Wilkinson, commanding the army, and Henry Dearborn, Secretary of War, both of whom had had firsthand experience with them in the last war.

Aside from the augmentation of April 1808 there was no further preparation for a fight until just six months before the second war with England. At that time, that is, in January 1812, Congress constituted ten new regiments of Regular infantry. The act of 11 January 1812 which created them was remarkable in at least two ways: first, it provided for the largest regiments and battalions authorized in the United States before the Civil War and, second, it established an organization that was at variance with the seven existing regiments. As a result, in the first six months of 1812 there were three different-sized infantry regiments, besides one of riflemen. The 1st and 2d regiments made up the infantry of the "military peace establishment," and they had ten companies in them of seventy-six enlisted men. The 3d through the 7th regiments, authorized in 1808, were called the infantry of the "additional force," and comprised ten companies with two more officers and two more enlisted men each than the 1st and 2d had. The 8th through the 17th in no way resembled the others, for they had eighteen companies of 110 enlisted men, arranged in two battalions.

Although some of the bulky eighteen-company regiments were raised, several never acquired their second battalions. Recruiting was so difficult that they lacked the time to raise many men before Congress voted a fresh reorganization. Late in June 1812, the legislators changed the law. According to the new arrangement there were to be twenty-five regiments of infantry, exclusive of the rifle regiment, each containing ten companies of 102 men. Thus all the infantry regiments were made uniform on paper, and a standard of organization was established that persisted throughout the conflict. This standard was more often than not honored in the breach. Once constituted, all the twenty-five regiments organized and recruited actively, but during the first two years of the struggle their efforts brought in less than half of the total number of infantrymen authorized.

Regulars at first could only enlist for five years, but late in 1812 newcomers were given a chance to enroll "during the war." All the while the states competed with the Federal government for soldiers, and the shorter "hitches" they offered drew men into their service. To combat this Congress directed the creation, in January 1813, of twenty new infantry regiments enlisted for just one year. Nineteen of them were raised and designated as the 26th through the 44th Infantry. Later, they were converted into long-term outfits (five years or the duration) , but all the units constituted after 1811 had men in them enlisted for different terms. For example, there were in a single regiment one-year regulars, eighteenmonth men, three- and five-year men, and some in for "during the war."

Early in 1814 four more infantry regiments and three more regiments of riflemen were constituted. Finally, therefore, forty-eight infantry regiments, numbered from the 1st to the 48th, came into being, plus four rifle regiments, the 1st through the 4th. This was the greatest number of infantry units included in the Regular Army until the world wars of the twentieth century. A mighty effort was made in 1814 to raise the Army to strength, and nearly 27,000 men came in, but in spite of this, four of the regiments had to be consolidated because they were too small. The 17th, 19th, 26th, and 27th were joined to form a new 17th and a new 19th, while the two highest numbered, the 47th and 48th, were redesignated the 27th and 26th, respectively.
No sooner was war over than Congress scrambled to rid itself of its more than 30,000 infantrymen. An act of 3 March 1815 set the peace establishment at 10,000 men, divided among infantry, rifle; and artillery regiments. Cavalry was eliminated, and eight infantry regiments and one rifle regiment arose from the ruins of the forty-six and four in existence. The rifles were consolidated and the infantry, after many rearrangements, settled as follows:

1st Infantry formed by consolidation of the 2d, 3d, 7th, and 44th

2d Infantry formed by consolidation of the 6th, 16th, 22d, 23d, and 32d

3d Infantry formed by consolidation of the 1st, 5th, 17th, 19th, and 28th

4th Infantry formed by consolidation of the 14th, 18th, 20th, 36th, and 38th

5th Infantry formed by consolidation of the 4th, 9th, 13th, 21st, 40th, and 46th

6th Infantry formed by consolidation of the 11th, 25th, 27th, 29th, and 37th

7th Infantry formed by consolidation of the 8th, 24th, and 39th

8th Infantry formed by consolidation of the 10th and 12th

The eight remaining infantry regiments were smaller than their war predecessors because, although the number of companies in each remained at ten, every company contained 78 men instead of 103. There was no effort to preserve the honors or traditional numbers of any of ,the prewar regiments. The 1st was merged with other regiments and redesignated the 3d, and the old 2d, 3d, 4th, 5th, 6th, and 7th were likewise lost in the remains of disbanded regiments. The new numbers were founded on the seniority of the colonels, the senior colonel commanding the 1st, and so forth. As a consequence of the reduction, 25,000 infantrymen were separated from the service. Another consequence was that the form of the infantry establishment was set roughly for the next thirty years. Not until the Mexican War, thirty-one years later, was it substantially expanded.