Unit 3 covers the great land-based empires 陆基帝国 of roughly 1450 to 1750. Four questions organise it: how they expanded, how they governed, how they paid for themselves, and how they used religion.

Expansion relied on the increased use of gunpowder, cannons, and armed trade - which is why these are often called the gunpowder empires 火药帝国. Access to gunpowder weapons let a central ruler overpower regional rivals and fortified nobles, so military technology and political centralisation grew together.

The empires to know:

• The Manchu (Qing) 满清 in Central and East Asia.
• The Mughal 莫卧儿 in South Asia.
• The Ottoman 奥斯曼 in the eastern Mediterranean and beyond.
• The Safavid 萨法维 in Persia.

Rulers faced the same problem: how to control territory far from the capital. The CED names the tools they used.

Recruitment of bureaucratic elites 官僚精英的选任 and the development of military professionals 职业军人 gave rulers officials who owed their position to the state rather than to birth. The clearest case is the Ottoman devshirme 德夫希尔梅 system, which recruited and trained administrators and soldiers, including the janissaries 耶尼切里; the Manchu continued China's examination system; the Safavids used ghulams 古拉姆.

Revenue came through tribute collection 纳贡, tax farming 包税制, and innovative tax-collection systems. The Mughal zamindar 柴明达尔 system and Ottoman tax farming are the standard examples, and the Ming practice of collecting taxes in hard currency 硬通货 is another.

Rulers continued to use religious ideas, art, and monumental architecture to legitimise their rule - Mughal mosques and mausolea, Ottoman mosque complexes, Qing imperial portraits, and European palaces such as Versailles all do the same work.

Religious change also produced conflict:

• The Protestant Reformation 新教改革 marked a break with existing Christian traditions and led to sustained religious and political conflict in Europe.
• Political rivalry between the Ottoman and Safavid empires intensified the Sunni-Shia split 逊尼派与什叶派分裂, showing how state rivalry can deepen a religious division.
• Sikhism 锡克教 developed in South Asia in a context of interaction between Hinduism and Islam.

Political and religious disputes together produced rivalries and conflict between states across Eurasia.

The unit's reasoning skill is comparison, and the productive comparisons are about method, not size:

• Recruiting officials by examination (Qing) against by enslaved-elite systems (Ottoman devshirme, Safavid ghulams).
• Tax farming (Ottoman) against land-revenue intermediaries (Mughal zamindars) against direct taxation (Ming hard currency).
• Legitimacy through religious identity (Safavid Shi'ism as state religion) against through tolerance of diversity (Mughal policy under Akbar).

Worked example (a real AP exam question). AP World short-answer questions in this unit typically ask students to "Explain one similarity" or "Explain one difference in how land-based empires maintained power." A full-mark answer names the method for both and explains the effect: "Both the Ottoman and Mughal empires used intermediaries to collect revenue rather than salaried tax officials, but the Ottomans used tax farming, which sold the right to collect for a fixed payment, while the Mughals relied on zamindars, hereditary landholders whose local standing gave them a permanent interest in the countryside." Notice the shape: the comparison is one function (raising revenue), performed two ways, with the consequence stated.

• Say why gunpowder mattered: it let central rulers overpower regional rivals, so military change and centralisation go together.
• Learn the four empires by their administrative method, not their territory - devshirme, examinations, zamindars, ghulams.
• Tax farming sells the right to collect; a zamindar is a hereditary landholder. Questions turn on that difference.
• Monumental architecture is evidence of legitimation, not decoration. Say what it was doing.
• The Ottoman-Safavid rivalry is the example of political conflict deepening a religious divide.
• Comparisons should be one function performed two ways, with the consequence stated.