The Bulgarians are an infantry and cavalry oriented civilization.
They are great at rushing, since their Militia-line infantry automatically upgrades upon advancing to the next age, while their team bonus enables their Blacksmith to rapidly upgrade their units. Also, these units retain their value as their unique technology Bagains gives their Militia-line Infantry +5 melee armor. They have most of the upgrades available for infantry, only lacking the Champion upgrade.
Their unique unit, the Konnik, is a cavalry unit that becomes an infantry unit when killed (with all of its implications). The strength of this unit relies on their durability, as they have to be killed twice, while they can also mess with the possible opponents' response to cavalry. They can be created at Kreposts, which are a fortification similar to a Castle, but weaker and cheaper (about half the price of a Castle). The attack speed of their cavalry can be improved with their Castle Age unique technology Stirrups. Regarding the Stable, they have all upgrades for the Hussar, but lack Paladin for the Knight line.
Defensively, they fare well thanks to the Kreposts and the fact that their Town Center costs 50 less stone, letting them save some stone for more fortifications.
Despite the fact that their Militia upgrades automatically and they have a unique technology that adds more armor to them, they still lack the Champion upgrade, which may make them vulnerable in the long run against well-rounded units or ranged units.
They can create Kreposts that can help defend their position, but lack several defensive technologies like Hoardings, Bombard Tower, Fortified Wall and Arrowslits, making them rely almost only on the Krepost for that purpose (which despite being cheaper than a Castle is still more expensive and takes longer to build than towers).
The Bulgarians are an infantry-oriented civilization, and as such, they may try an infantry Feudal Age rush in the early game, which is particularly potent in their case. At the very beginning of the game, the Bulgarians do not have any bonuses (apart from their automatic improvement of their Militia line). As such, their build order for an infantry rush is very similar to most other civilizations, and they should try to advance to the Feudal Age as soon as possible. In this sense, the Bulgarian player must start to produce their Militia in the Dark Age, so when advancing to the Feudal Age, they will be ready to raid an opponent, who will hardly have the right counter-units for Men-at-Arms. Once in the Feudal Age, Bulgarians should create a Blacksmith (which for them works faster), research the infantry improvements there, and create additional Barracks to spam more Men-at-Arms. Bulgarians are not very flexible in terms of strategy in the early stage of the game, so they are predictable. When playing against Bulgarians, the player must hurry up to Feudal Age as well and prepare Archers, Towers, or turtle themselves in order to avoid their Men-at-Arms rush.
Bulgarians are probably at their peak in the Castle Age, when their bonuses start to really kick in. Once in the Castle Age, they will get access to the Krepost, cheaper Town Centers, their unique unit the Konnik, and, of course, their Men-at-Arms will be upgraded to Long Swordsmen. Some effective strategies a Bulgarian player should take into consideration is a Krepost Drop, Konnik rush or a Knight rush. In any case, a Fast Castle must be made first. In the first two cases, the player must gather stone beforehand.
For a Castle Age Krepost Drop, the player should in theory research Masonry, Murder Holes, and Ballistics at the University, as well as researching Fletching and Bodkin Arrow at the Blacksmith, but players rarely have so much resources in the Castle Age. Kreposts are very similar to a Castle, but weaker and cheaper. They also are created faster and cannot research technologies or train Trebuchets or Petards (so one castle will still be required to upgrade their Konniks to Elite, research their Castle technologies, and train Trebuchets in the Imperial Age). Since Kreposts are cheaper (about half the price of a Castle), the Bulgarian player may place two of them near each other to provide cover fire and start spamming Konniks. Krepost are also useful for turtling and defending locations, but the player must have in mind that they have less range, hit points, and attack than Castles, but the convenience that they can make almost two of them for the same price. Krepost are also useful when performing the Konnik rush, since having two of them instead of one Castle naturally means they can create Konniks faster. The Krepost also count as a "Castle" regarding the requirements for aging up to the Imperial Age, and this may also enable the Bulgarians to perform a Fast Imperial Age strategy, since they require much less stone and less time to built than Castles. In addition, a Krepost near the main base of the enemy will often mean a good psychological advantage, even though it does not have to absolutely win the game by itself.
Regarding the Konnik rush, this unit has the advantage that it has to be killed twice, since they become dismounted Konniks when die. Not only are they durable, but in many circumstances, it is hard to respond to a Konnik raid, since the armor class of the unit changes to infantry, so the typical counters for cavalry does not affect the dismounted version of this unit. Also, if the Konniks are caught by the opponent's arrow-fire and killed, the Dismounted Konniks will automatically go and harass the nearest opponent unit or building. Because of this quirk, a Konnik rush should be preferred over a Knight rush, unless the player doesn't have enough stone for making enough Castles or Kreposts. The Stirrups technology also makes the Konniks more appealing, since it increases the attack speed of the mounted version of the unit, and also the attack speed of the Light Cavalry.
In the Imperial Age, they must keep using their infantry and Konniks and support them with Hussars, especially when entering the "trash wars". Their Imperial Age unique technology Bagains grants +5 melee armor to the Militia line, so their Two-Handed Swordsmen become more effective against melee units. Sadly, they lack the Champion upgrade, but Bagains is a good replacement for that.
In update 36906, the Bulgarians lose the Paladin upgrade, but Stirrups affects all cavalry units. This in turn shifts the Bulgarian power spike from the Imperial Age to the Castle Age, as the Bulgarian Knight rush is much stronger. Conversely, the loss of Paladins means that the Bulgarians will lose much of their late-game cavalry power, forcing the Bulgarians to mostly rely on Konniks and Hussars as their main late-game cavalry units.
In update 42848, the Bulgarians' team bonus towards Blacksmith work rates is changed from 50% to 80%. In addition, a new unique bonus discounts the food costs of Blacksmith and Siege Workshop technologies by 50%, allowing the Bulgarians to easily afford Imperial Age siege upgrades, and providing a food boost in late Feudal and early Castle Age, while also making it much easier to fully upgrade their Konniks.
The Bulgarians are valuable allies not only for their team bonus, but also because they are great at raiding in the early and mid game and can help defend the team by placing Kreposts in strategic spots and aid defending players.
The effect of Bulgarians' team bonus is that allied Blacksmiths research faster, which comes very handy for most civilizations, but among all of them the most favored are the eight civilizations with full Blacksmith upgrades (Berbers, Britons, Chinese, Italians, Portuguese, Saracens, Spanish, and Turks), the Incas, as they get extra armor and attack for their Villagers out of Blacksmith technologies, and the Bohemians, whose Blacksmiths only costs 50 wood and only lack Plate Barding Armor. Probably the best three civilization synergies that can be done with the Bulgarian team bonus are with Spanish, Incas, and Chinese. An alliance with Incas will enable the Incan player to better perform their Tower rush and Villager rush. An alliance with Spanish, considering their Blacksmith upgrades does not cost any gold, enables the Spanish to outperform many other civilizations, especially when performing their signature tactics (like the Knight rush or raiding with Conquistadors). Similar logic can be applied to the Chinese, as they get overall cheaper technologies. Having a Bulgarian ally may aid the Bengalis to upgrade their Rathas, as that unique unit needs both melee and pierce attack improvements at the Blacksmith.
As a civilization specialized in cavalry, Bulgarian players also benefit from other team bonuses, such as efficiency-enhanced stables from Hunnic allies, vision bonus for Knight-line units from Frankish allies, anti-archer bonus for Knight-line units from Persian allies, and extra conversion resistance from Teuton allies. Considering that their scout line are enhanced with the Stirrups technology, they can be also boosted with the Mongolian team bonus that gives them +2 LOS, or anti-archer bonus(+1 attack) from Polish teammates. Anti-building bonus (+2 attack) from a Hindustani team-mate also helps.
The Bulgarian team bonus can be combined on a team with the Malian and Lithuanian team bonuses, making teams like these outclass their opponents by rapidly research their technology trees. Also, a Berber ally may add the Kasbah technology to this formula.
Since the Bulgarian Militia line upgrades for free and also get Bagains as an upgrade for them, Infantry team bonuses may also be considered. Among them, the Goth team bonus is probably the most useful, since it makes the Barracks work faster.
Since Bulgarians might have a problem dealing with heavy mass ranged units in the late-game, it is a good idea to have an ally who produces strong ranged units and fully upgraded skirmishers. The only good answer to mass archers or cavalry archers in the late game is Siege Onager + ram, since the Bulgarians do not have the last archer armor technology. Of course, it is a problem to keep making Konniks while researching the Siege Onager technology, which is very expensive. Also, some players massing archers and keeping them alive since the Feudal Age might quickly snowball a Konnik/infantry composition easily.
The Slavs can also be considered a great offensive partner for a Bulgarian player, as both rely on infantry, with their Slav-Bulgarian Barracks providing +5 population and their Blacksmith working 50% faster, combined with the Konniks and Boyars, and their infantry benefit from Druzhina and Bagains respectively.
Compared advantages and disadvantages
Advantages vs other civilizations
Disadvantages vs other civilizations