In Nelson's day there were six 'rates' of warships, the 1st rate being of 100 guns or more, down to the sixth rate with 20 or more guns. The first four rates were 'line-of-battle' ships although during the period 1793-1815, 4th rates were considered too small to stand in the line of battle. 5th and 6th rates were the frigates - 'the eyes of the fleet'. There were also a variety of unrated vessels - less than 20 guns.

The Line of Battle
The idea of going into battle with ships drawn up in line one behind the other was introduced durinng the Anglo-Dutch wars. This system enabled ships to deliver a succession of broadside against an enemy with great effect. It proved so effective that other nations followed. However, stringent adherence to this pattern often led to inconclusive results.

Nelson did not always stick to this set line-of-battle. He was a brilliant naval tactician and sometimes used unconventional methods. His example encouraged the use of initiative and inspired his officers.

1st Rate Ships
3 deckers, of 100+ guns. They provided accommodation large enough for an admiral and his staff. The additional deck allowed an extra set of cabins at the stern where the admiral could live in some splendour. The third deck meant higher sides and thus poor sailing qualities but these were compensated for by the increase in broadside weight. Often, 1st rate ships had longer lives because they were so expensive to build they were in consequence kept in good repair.

2nd Rate Ships
Some 3-deckers fell into this category. They had 86-98 guns.

3rd Rate Ships
The majority of ships-of-the-line in all fleets were 3rd rates. They carried between 62 and 84 guns on two decks.

The larger types of ships in this rate, of 80 or more guns, had a gun power almost equal to a 3-deck 98 gun ship. Several of the 80 gun ships in the British fleet were captured from the French.

74 gun ships, the most common ship-of-the-line, made up about half the line-of-battle ships in the navy list. Well proportioned vessels with good sailing abilities and strong gun power.

64 gun ships, the second biggest class of ship-of-the-line. Not popular with naval officers, although Nelson always maintained that the Agamemnon (64) had been his favourite ship.

4th Rate Ships
This was a relatively small group of two deck vessels of 44 to 60 guns. Few were built after 1750, although some were converted from East India Co vessels.

5th Rate Ships (Frigates)
A large group of single decked ship rigged vessels, from 32 to 44 guns.

6th Rate Ships (Frigates)
Also single decked ship rigged vessels, 20-30 guns.

Both 5th and 6th rate ships were large enough to be used for reconnaissance, commerce raiding and escort duty. These were the smallest vessels to be commanded by a post captain.

Unrated Vessels
With complements of less than 20 guns.