Also known as 'assault boots' or simply 'army boots', combat boots are the footwear upon which an army marches, fights, and does all the other things that an army does. The first specialised military shoes were developed, as were so many other things, by the Romans; '
caligae', made of several layers of tanned leather, were unfortunately forgotten after the collapse of the Roman empire. From then until
the 1700s soldiers were expected to fight in their own shoes, as even European armies were generally low-budget affairs in which it was feared that soldiers would join up for the shoes, and then
desert.
Hard as it is to believe, heels were not invented until the 1600s, a period which coincided with the first post-Roman standing armies. A history of armies in general is outside the scope of this writeup; suffice it to say that the British redcoat of the mid-1700s was equipped with leather, buckled, pointed shoes in which he marched, fought and died, in that order. They were not proper boots, however, and were more suited for the parade ground than actual down-and-dirty fighting of the sort found in the war of independence.
During the Napoeleonic wars of the 19th century Prince Gebhard von Blucher developed the 'Blucher boot', recognisable to modern eyes as a combat boot, and by World War One one or more pairs of proper stomping boots were standard issue to armies of the western world. Either black or brown, they were required to be water resistant, comfortable, and sturdy; this latter attribute often took precedence over the former, as sturdy boots could be stripped from the corpses of the dead and reused, thus saving money. By the end of the first day of the Battle of the Somme the British Army found itself with 20,000 surplus boots, and one of the less attractive jobs for a soldier involved wading into no man's land to go and collect them.
In that conflict the troops often spent their days in rainswept muddy trenches, which led to 'trench foot', a preventable infection which was eventually made a chargeable offence. Waterproof boots could only protect the soldier from ankle-deep mud, however, and even in the modern age of armoured personnel carriers a variety of gaiters and ties exist for soldiers in damp environments.
It was during the great war and shortly afterwards that the phenomenon of Army surplus stores came into being (known in the UK as 'Army and Navy Stores', the term dating from before the Royal Flying Corps was large enough to have its own gear). Hitherto, the British Army had been a small, professional force, one which had magnificently fought into oblivion by 1916. It was followed by 'Kitchener's Army' - a mass produced conscript force supplied, for the first time, by industrial mass production. Even more than before, war become a conflict between factories, and large quantities of excess supplies were generated by rapid demobilisation. Much of this supplied European armies until World War Two, after which another round of demobilisation, followed by the disbandment of empires, has kept army surplus stores in kit ever since. In Britain one can still find World War Two gas masks for sale in such shops, although they contain asbestos and are not recommended for use (mid-50s cold war masks are useful, however, provided one has a fresh filter).
Combat boots are the basic commodity of such stores, as they last for years and every single serviceman is equipped with at least one pair, which he or she was required to keep clean and polish to a mirror finish as an aid to discipline (this sadistic practice was known as 'bullshine' or 'bulling', although the troops no doubt used another word beginning with 'bull').
Although the boot was in its modern form by 1918, there were still some refinements left. By World War Two most armies used a variation of the 'Brogan' boot, similar in appearance to a regular work shoe, only going up to the top of the foot. American paratroopers were issued with 'Corcoran' cavalry-style jump boots, used in the inter-war years by motorcycle policemen and derived from boots worn by obsolete cavalry soldiers. These were waterproof, shockproof, ran right up the ankle and were greatly loved, eventually becoming the standard, although the British army took until the 1970s to adopt a high-leg boot. For general service modern boots are much the same as they have been since the 1950s - leather uppers, lined, hard sole, lots of laceholes, comfortable when worn with thick socks and insoles. The majority of army boots have rubber soles (DMS, or 'Direct Moulded Sole', not to be confused with 'DMs', Doctor Martens). In Britain at least certain units, especially the more ceremonial, are issued with 'ammo boots', which have leather soles festooed with hobnails and metal plates. These were standard issue until WW2, the hobnails serving to protect the leather from wear. Hobnailed boots make a very loud noise and can produce sparks, but are otherwise very impractical, with poor grip on slippery surfaces and a tendency to damage flooring. 'Ammo boots' is actually a misnomer, actual ammo boots being steel-toed with a rubber sole, as as not to ignite stray powder.
For jungle or desert environments boots are typically made with a deeper tread pattern and canvas uppers, the arches being ventilated to prevent foot-rot. Jungle boots are therefore not waterproof, the philosophy being that such a goal would be futile in the jungle, and that it is better to design a boot which can let out water quickly. The more expensive boots are nowadays made with Goretex, a synthetic wonder fabric that is both waterproof and breathable, whilst servicemen who are not expected to do a lot of walking - sailors, pilots, drivers and so forth - are often issued with lightweight, thin-soled boots. During the Vietnam conflict, American jungle boots incorporated a metal 'anti-spike' plate embedded into the sole, although even the toughest boots are no match for an anti-personnel land mine.
Being tough, combat boots require breaking in before they can be worn comfortably (unissued ones in particular, although used boots will still require familiarisation, unless one's feet and weight are the same as the previous owner). In service this usually involves trudging through mud whilst wearing them constantly, not least because punished feet tend to swell up outside the constraints of boots, making them harder to put back on. Keeping boots and socks dry has taxed the minds of soldiers since time immemorial; although socks can be warmed and dried by storing them in the crotch or armpit area of one's trousers, boots are trickier to dry unless one has the warm engine of a tank nearby, or possibly a horse. Boots with a soft inner lining are more comfortable and warmer than those without, but absorb more water.
Combat boots have often been objects of controversy. Either one's own army is unable to supply them in sufficient quantities or common sizes, or the 'other side' has better boots. This leads to enemy battlefield casualties being quickly stripped of their footwear (Falklands War footage of Argentine corpses often shows them with bare feet, their footwear being warmer and more comfortable than the spartan, ankle-length British boots of the time). The state of the British Army's footwear in the late hostilities with Iraq is an ongoing affair, the standard issue desert boots being found to melt in hot weather.
Army surplus boots are popular with civilians, although they are to some extent the footwear equivalent of SUVs, in that are bought mainly for their visual and psychological impact. Combat boots tend to have hard, flat soles which make them unsuitable for running. Being waterproof, they are often uncomfortably sweaty when worn indoors. For hiking or long walks combat boots are superb provided one fits suitable insoles, but dedicated hiking boots are usually more comfortable and do not require breaking in. Indeed members of the better-equipped, more laissez-faire army units, such as the Special Air Service, prefer to buy their own footwear. Furthermore, as a symbol of viscious intent, yellow-stitched Doc Martens are more potent than relatively anonymous black leather boots. Combat boots are nonetheless useful and extremely durable jacks-of-all-trades. They can be worn with formal wear, and they are extremely good value for money. They are easily cleaned and polish up to a neat shine. Perhaps best of all, they circumvent fashion entirely.
Combat is the last thing combat boots are used for; the image of a soldier kicking down a door, bayonet at the ready, is outdated in an age of metal shotgun slugs and breaching charges. For a long time during the Cold War soldiers were not even expected to march in their boots, as they were to be carried into the technological battlefield aboard helicopters and infantry fighting vehicles. The shift from all-out electro-technical heavy metal nuclear war to policing, anti-insurgency and 'operations other than war' has shredded this simplistic thinking, however, and in countless modern conflicts soldiers in the first, second and third worlds have patrolled, walked, and ran into battle, a situation which seems likely to continue forevermore.
Much respect to a similar, excellent feature on H2G2, which covers British army boots in more detail, and has a particularly interesting method of breaking boots in:
http://www.bbc.co.uk/dna/h2g2/A878024