I was reading about impressment as it pertains to the War of 1812 and the British using it to crew its warships. It states that it "refers to the act of taking men into a military or naval force by compulsion" but does not give any concrete examples how they enforced it or what the consequences were for people who tried to disobey. Was it basically treated like being drafted or conscription? Specifics would be greatly appreciated!
What you're talking about is referred to as impressment in the time period -- you may have heard of "press gangs" or, in a later era, people being "shanghaied" into merchant service. These tend to be conflated in the popular mind but are somewhat distinct in practice.
Impressment, in general, is the idea that subjects of the Crown owed service or fealty to the Crown when needed, whether collectively (as in, this port town furnishes ships/money/men/whatever) or individually (this group of people is subject to service when called). The term comes from the imprest, sometimes called prest money, that impressed sailors would usually receive upon being called to serve. (Imprest is technically any money lent to, say, an official, or soldier/sailor, before their term of service, meant to be binding on their service.)
Now, as to how impressment actually worked, well, it varied over time and with the manning requirements of the Navy. In, say, the Elizabethan navy, the "navy" as a fleet of fighting vessels was still comprised largely of private ships in the Queen's service; the "Navy Royal" might have been ships owned directly or partially by the queen herself, but the "navy" was supplemented by private men-of-war taken up into a larger organization temporarily; the assumption was that they solved their own manning problems. The change in impressment and growth in impressing individual sailors was generally related to booms and busts in manpower needs as the English, later British, navy became fully equipped by the state.
The basic problem with the theory of impressment is that it assumed there were enough mariners in England/Britain to meet the needs of the fleet, and that they would gladly serve if impressed. In fact, there were never enough seamen in Britain to man the fleet entirely with them, and in any case snapping up every seaman would mean the merchant fleet would grind to a halt (and in fact there were exemptions from impressment for men who served as fishermen, in colliers, in portions of the merchant fleet, etc.) Over time, press gangs became less choosy about the type of men they impressed.
I'm going to quote myself from this previous answer:
In theory, the impress service or impressment was supposed to take men who had "had use of the Sea," which would have limited it to people who had been aboard before. In practice, the impressment of each war or crisis worked out somewhat differently:
- in the Dutch wars of the 1650s-1680s, men would be pressed for a season, and could generally be counted to show up when they were meant to and to serve for the year aboard a ship. (The "press" or "impress" they received was actually an advance on pay that they would receive upon promising to show up for a ship.) As the Dutch wars continued and the Navy got larger, impressing just a portion of the men in the merchant or fishing services became less likely to work, and men started to resist the press, either actively (by running/not showing up once pressed) or passively (by avoiding press gangs).
- In the press that existed in the Seven Years war, pressed men started to be used aboard ships for longer periods of time (because the Navy started keeping ships in active service for longer). That led to more unrest for the men, who particularly disliked being turned over from one ship into another (in general, men were paid at the end of each deployment, with deductions for slops [clothes] and medicine they used during the deployment). When they were turned into another ship, they would be paid off for service in that ship only, and would receive a "ticket" for their other service which had to be cashed in London. In practice, most sailors were unable to go to London to cash it (and ran the risk of being pressed again), so they wound up selling their tickets at a discount.
- By the time of the French Revolutionary and Napoleonic wars, impressment was a major way to man the Navy. Popular and successful captains generally were able to man their ships with volunteers, while others had to rely on the press gangs. Those men grew less seamanly as the sale of the press increased and the manpower needs of the Navy increased, and the pressed men compounded the problems (or vice versa) faced by unpopular captains.
The social unrest that impressment caused or added to changed over time, as well. I'm also going to quote from this answer for a bit:
There wasn't a satisfactory solution to the manning problem at any point during the period you mentioned. Impressment (the "press gangs" of lore) was a partial solution, but press gangs were often hated by local authorities and resisted, and had other problems besides (the most pertinent being the varied quality of those they impressed). One of the major problems the navy faced was how to encourage the growth of the seafaring classes (by making fishermen, colliers, and seamen involved in other trades) exempt from impressment, but those were often guided by political rather than necessarily logical interests.
The manning problem became more acute after the Dutch wars because the campaigns agains the Dutch were short and seasonal. The wars of the Spanish succession were fought over the course of several years, and the manning requirement was substantially larger due to that. The contemporary understanding of the problem assumed that there were enough seamen to fill all the needed spots in the navy and the issue was finding the men, but later research has proved that to be wrong -- no matter what, the navy would have to employ a substantial number of landmen to fill unskilled jobs. A major solution to the manpower problem was the revival of the Marine regiments, which were re-formed in 1702. The Marines were useful both as soldiers in landing expeditions (such as the capture of Gibraltar) and also as unskilled labor. Marine battalions were originally simply sailors embarked on ships, but the Royal Marines became a distinct service in 1755.
The French solution to their manning problem was its systeme des classes, a registration of seamen in coastal areas to serve 1 year out of every 3, but it was not a solution that would work in Britain with its strong tradition of "English liberty." Even a voluntary registration of seamen proposed in 1749 was denounced as tending to enslave Britons. So the press gang was seen as a lesser evil as long as it impressed only seamen. By the mid-1740s, the "Impress Service" covered most of England, but it was more efficient in some localities than others due to varying degrees of resistance from local authorities.
The flip side of the manning problem was managing desertion, which was most often a problem when men were not long-term members of a settled ship's company or when men who were were transferred to a new (unfamiliar) ship without their consent. In those cases, they most often deserted back to their old ship and officers.
As a consequence of the extended wars of the early 16th century, the Navy had more men under arms than ever before. Impressment and transfers of men from one ship to another also inevitably threatened the social contract under which most ships worked. This then led to more strain on the administrative structures of the navy, and the Admiralty released a set of Regulations and Instructions relating to his Majesty's Service at Sea in 1731. Many of the regulations dealt with accounting aboard ships (relating to public money and public stores), but they also regulated the daily routine of ships, from cleaning to cooking to discouraging blasphemy. This had the long-term effect of making more similar what men could expect from ships' companies across the Navy.
A major innovation during the Seven Years' War (1754-63) was the creation of the divisional system, which was popularized (and maybe invented by) Vice-Admiral Thomas Smith. The system divided a ship's company into divisions allocated to lieutenants and warrant officers, who would be directly responsible for the men under their command. This had the effect of making sure that even in the largest ships, men would be known to at least one officer. That relationship was crucial in creating humane relations that were essential to discipline.
Here are some other threads about impressment that I've contributed to:
https://www.reddit.com/r/AskHistorians/comments/2oo91z/during_the_age_of_sail_how_reliable_were/