Nobunaga's Ambition is a historical simulation-RPG-strategy game that was developed by Yoichi Erikawa, the founder of Koei. Erikawa had initially developed the game as a hobby alongside running Koei, which at the time was a chemical wholesaler. However, when he finished the game and had it published, it became such a smash success that Erikawa converted Koei into a video game studio and set to work on video games full-time. For his future projects, Erikawa took on the pen name Kou Shibusawa. Originally released on the PC, versions have also been produced for the NES, Genesis, Game Boy and numerous others.
Nobunaga's Ambition is the first in a long-running series of historical strategy games set against Japan's Warring States era. Its title refers to Nobunaga Oda, one of the most powerful warlords of the era, who was on a path to unifying Japan under his rule until his assassination in 1682. In the game, the player attempts to do what Nobunaga could not, and unite all of Japan.
As the title suggests, the player is tasked with achieving the ultimate goal of warlord Oda Nobunaga; the conquest and unification of Japan. Selecting Oda Nobunaga is optional, however, as the player is also able to choose from a variety of other regional daimyos of the era.
The player may choose from four campaign scenarios including:
- Battle for the East (beginning in 1560)
- Daimyo Power Struggles (1560)
- Ambition Untamed (1571)
- Road Towards Unification (1582)
In each scenario, the player must first select a daimyo to play as, and also determine the daimyo's statistics, which are defined by Health, Ambition, Luck, Charm, and IQ. Each statistic is ranked on a hundred-point scale. The progression of time is structured in a turn-based manner. When in the map view, the passing of a turn corresponds to a change in season, and each turn during battle corresponds to the passing of a single day. As time passes, daimyos and officers age and will eventually die of natural causes. As the game progresses, the player must allocate resources to raise a capable military force, encourage a productive economy to support both military and civilian expansion, and support the peasants in order to sustain their respect and loyalty.
Battles take place in maps that are divided into 5x10 grids with terrain types such as hills, mountains, villages, rivers, plains, and castles. The player may achieve victory in battle through numerous means, among which include forcing the enemy to retreat, destroying the enemy command unit, outlasting an invading force, or prolonging battle until the opposing force has exhausted its supplies.
Outside of battle, the player can make numerous decisions that affect domestic and diplomatic policy as well as military decisions that affect troop strength and allocation. Such actions include transporting soldiers, rice and gold between fiefs, which can be used to strengthen regions at the expense of others. Taxes may be raised or lowered to adjust the income level and the land may be cultivated to boost productivity, though raising taxes or choosing to cultivate will also lead to a decrease in loyalty among the peasants. Expanding a town allows for greater tax income, as well, but also leads to a reduction in loyalty. If loyalty drops too low, the peasants may rise up in rebellion.
To ward against floods, the player can adjust the level of flood control, though the higher the control, the lower the productivity. It is also possible to recruit soldiers or ninja for the military, train the troops, and provide rice to the peasants and troops as a means to raise morale. On the diplomatic side, in addition to going to war, it is also possible to encourage good relations between rival factions by ratifying a non-aggression pact or arranging a marriage. Alternatively, the player can also send spies to keep tabs on rivals or work to win over a rival's own peasants. Merchants can be approached in order to buy weapons, buy or sell rice, or borrow money. It is also possible for the player character daimyo to fall ill, and so if necessary, the player may need to spend time to recuperate.
If a player does not wish to control every aspect of governing, it is also possible to allow the computer AI to govern aspects of selected fiefs.
Evan Brooks of Computer Gaming World enjoyed the game greatly, and in the September 1988 issue rated it as "Highly Recommended." In his review, he noted, "This reviewer was glued to his computer for 13 hours, stopping at 3:00 am. Not since Gunship has this occurred. The end result is that the computer gamer must have, at least, one Koei game in his inventory!"