Cavalry
During the 18th century however the Ottoman mounted troops evolved into light cavalry serving in the thinly populated regions of the Middle East and North Africa. Such frontier horsemen were largely raised by local governors and were separate from the main field armies of the Ottoman Empire. At the beginning of the 19th century modernised Nizam-I Credit ("New Army") regiments appeared, including full-time cavalry units officered from the horse guards of the Sultan.

Renaissance Europe: Ironically, the rise of infantry in the early 16th century coincided with the "golden age" of heavy cavalry; a French or Spanish army at the beginning of the century could have up to half its numbers made up of various kinds of light and heavy cavalry, whereas in earlier medieval and later 17th-century armies the proportion of cavalry was seldom more than a quarter.
Knighthood largely lost its military functions and became more closely tied to social and economic prestige in an increasingly capitalistic Western society. With the rise of drilled and trained infantry, the mounted men-at-arms, now sometimes called gendarmes and often part of the standing army themselves, adopted the same role as in the Hellenistic age, that of delivering a decisive blow once the battle was already engaged, either by charging the enemy in the flank or attacking their commander-in-chief.
From the 1550s onwards, the use of gunpowder weapons solidified infantry's dominance of the battlefield and began to allow true mass armies to develop. This is closely related to the increase in the size of armies throughout the early modern period; heavily armored cavalrymen were expensive to raise and maintain and it took years to train a skilled horseman or a horse, while arquebusiers and later musketeers could be trained and kept in the field at much lower cost, and were much easier to recruit.

The Spanish tercio and later formations relegated cavalry to a supporting role. The pistol was specifically developed to try to bring cavalry back into the conflict, together with manoeuvres such as the caracole. The caracole was not particularly successful, however, and the charge (whether with lance, sword, or pistol) remained as the primary mode of employment for many types of European cavalry, although by this time it was delivered in much deeper formations and with greater discipline than before. The demi-lancers and the heavily armored sword-and-pistol reiters were among the types of cavalry whose heyday was in the 16th and 17th centuries. During this period the Polish Winged hussars were a dominating heavy cavalry force in Eastern Europe that initially achieved great success against Swedes, Russians, Turks and other, until repeatably beaten by either combined arms tactics, increase in firepower or beaten in melee with the Drabant cavalry of the Swedish Empire. From their last engagement in 1702 (at the Battle of Kliszów) until 1776, the obsolete Winged hussars were demoted and largely assigned to ceremonial roles. The Polish Winged hussars military prowess peaked at the Siege of Vienna in 1683, when hussar banners participated in the largest cavalry charge in history and successfully repelled the Ottoman attack.

18th-century Europe and Napoleonic Wars: Cavalry retained an important role in this age of regularization and standardization across European armies. They remained the primary choice for confronting enemy cavalry. Attacking an unbroken infantry force head-on usually resulted in failure, but extended linear infantry formations were vulnerable to flank or rear attacks. Cavalry was important at Blenheim (1704), Rossbach (1757), Marengo (1800), Eylau and Friedland (1807), remaining significant throughout the Napoleonic Wars.

Even with the increasing prominence of infantry, cavalry still had an irreplaceable role in armies, due to their greater mobility. Their non-battle duties often included patrolling the fringes of army encampments, with standing orders to intercept suspected shirkers and deserters, as well as, serving as outpost pickets in advance of the main body. During battle, lighter cavalry such as hussars and uhlans might skirmish with other cavalry, attack light infantry, or charge and either capture enemy artillery or render them useless by plugging the touchholes with iron spikes. Heavier cavalry such as cuirassiers, dragoons, and carabiniers usually charged towards infantry formations or opposing cavalry in order to rout them. Both light and heavy cavalry pursued retreating enemies, the point where most battle casualties occurred.
The greatest cavalry charge of modern history was at the 1807 Battle of Eylau, when the entire 11,000-strong French cavalry reserve, led by Joachim Murat, launched a huge charge on and through the Russian infantry lines. Cavalry's dominating and menacing presence on the battlefield was countered by the use of infantry squares. The most notable examples are at the Battle of Quatre Bras and later at the Battle of Waterloo, the latter which the repeated charges by up to 9,000 French cavalrymen ordered by Michel Ney failed to break the British-Allied army, who had formed into squares.

Massed infantry, especially those formed in squares were deadly to cavalry, but offered an excellent target for artillery. Once a bombardment had disordered the infantry formation, cavalry were able to rout and pursue the scattered foot soldiers. It was not until individual firearms gained accuracy and improved rates of fire that cavalry was diminished in this role as well. Even then light cavalry remained an indispensable tool for scouting, screening the army's movements, and harassing the enemy's supply lines until military aircraft supplanted them in this role in the early stages of World War I.

19th century: 

Europe: By the beginning of the 19th century, European cavalry fell into four main categories:

Cuirassiers, heavy cavalry, adorned with body armor, especially a cuirass, and primarily armed with pistols and a sword
Dragoons, originally mounted infantry, but later regarded as medium cavalry
Hussars, light cavalry, primarily armed with sabres
Lancers or Uhlans, light cavalry, primarily armed with lances

There were cavalry variations for individual nations as well: France had the chasseurs à cheval; Prussia had the Jäger zu Pferde; Bavaria, Saxony and Austria had the Chevaulegers; and Russia had Cossacks. Britain, from the mid-18th century, had Light Dragoons as light cavalry and Dragoons, Dragoon Guards and Household Cavalry as heavy cavalry. Only after the end of the Napoleonic wars were the Household Cavalry equipped with cuirasses, and some other regiments were converted to lancers. In the United States Army prior to 1862 the cavalry were almost always dragoons. The Imperial Japanese Army had its cavalry uniformed as hussars, but they fought as dragoons.
In the Crimean War, the Charge of the Light Brigade and the Thin Red Line at the Battle of Balaclava showed the vulnerability of cavalry, when deployed without effective support.

Franco-Prussian War: During the Franco-Prussian War, at the Battle of Mars-la-Tour in 1870, a Prussian cavalry brigade decisively smashed the centre of the French battle line, after skilfully concealing their approach. This event became known as Von Bredow's Death Ride after the brigade commander Adalbert von Bredow; it would be used in the following decades to argue that massed cavalry charges still had a place on the modern battlefield.

Imperial expansion: Cavalry found a new role in colonial campaigns (irregular warfare), where modern weapons were lacking and the slow moving infantry-artillery train or fixed fortifications were often ineffective against indigenous insurgents (unless the latter offered a fight on an equal footing, as at Tel-el-Kebir, Omdurman, etc.). Cavalry "flying columns" proved effective, or at least cost-effective, in many campaigns—although an astute native commander (like Samori in western Africa, Shamil in the Caucasus, or any of the better Boer commanders) could turn the tables and use the greater mobility of their cavalry to offset their relative lack of firepower compared with European forces.
In 1903 the British Indian Army maintained forty regiments of cavalry, numbering about 25,000 Indian sowars (cavalrymen), with British and Indian officers.
Among the more famous regiments in the lineages of the modern Indian and Pakistani armies are:

Governor General's Bodyguard (now President's Bodyguard)
Skinner's Horse (now India's 1st Horse (Skinner's Horse))
Gardner's Lancers (now India's 2nd Lancers (Gardner's Horse))
Hodson's Horse (now India's 3rd Horse (Hodson's)) of the Bengal Lancers fame
6th Bengal Cavalry (later amalgamated with 7th Hariana Lancers to form 18th King Edward's Own Cavalry) now 18th Cavalry of the Indian Army
Probyn's Horse (now 5th Horse, Pakistan)
Royal Deccan Horse (now India's The Deccan Horse)
Poona Horse (now India's The Poona Horse)
Scinde Horse (now India's The Scinde Horse)
Queen's Own Guides Cavalry (now Pakistan).
11th Prince Albert Victor's Own Cavalry (Frontier Force) (now 11th Cavalry (Frontier Force), Pakistan)
Several of these formations are still active, though they now are armoured formations, for example the Guides Cavalry of Pakistan.