How did nationalism threaten the existing political order of the nineteenth century?

Is there something about this question you do not understand? What does your textbook say?

single most powerful European political ideology of the 19th and early 20th centuries

political outlook, nationalism was and is based on the relatively modern concept that a nation is composed of people who are joined together by the bonds of common language

as well as common customs, culture, and history
bonds should be administered by the same government, nationalists in the past and present contend that political and ethnic boundaries should coincide

belief that one is part of a nation, defined as a community with its own language, traditions, customs, and history that distinguish it from other nations and make it the primary focus of a person's loyalty and sense of identity

Okay, so how is this different from earlier ways of thinking? What was the existing political order? What was it based on? Military power? Religion? What?

The political order of the 19th century, at the time combined people of many nationalities who wanted their own governments.

Nationalism threatened the existing political order of the nineteenth century in several ways. To understand why, we need to analyze the key features of nationalism and its impact on the existing political order.

The main premise of nationalism is the belief that loyalty and devotion to one's nation or ethnic group should be the primary focus of individuals, surpassing other loyalties such as those based on religion, class, or monarchy. This idea posed a challenge to the traditional political structures that dominated much of the nineteenth century, which were often based on monarchies, empires, or other forms of hierarchical rule.

1. Disruption of established empires: Nationalism challenged the legitimacy of multinational empires that incorporated diverse ethnic or cultural groups. These empires, such as the Austro-Hungarian Empire or the Ottoman Empire, were often held together by force or strategic alliances. Nationalist movements within these empires sought to establish independent nation-states based on shared cultural or ethnic identities, leading to the disintegration of large empires.

2. Calls for self-determination: Nationalism promoted the idea that every nation had the right to govern itself. This desire for self-determination offered a new perspective that differed from traditional notions of legitimacy tied to inherited rulers or conquest. It sparked movements for independence such as the Greek War of Independence (1821-1832) or the Italian Risorgimento (1815-1871). These movements sought to establish unified nations based on shared cultural or linguistic characteristics, challenging the existing political order.

3. Spread of revolutionary ideologies: Nationalist ideas often intertwined with other revolutionary ideologies of the time, such as liberalism or socialism. The belief in the sovereignty of the people and the desire for political representation fueled demands for constitutional reforms and the weakening of existing power structures. Nationalistic aspirations often aligned with these ideologies, creating a potent force that threatened the established political order.

4. Ethnic conflicts and territorial disputes: Nationalism also brought to the forefront various ethnic conflicts and territorial disputes, especially in regions where different ethnic or national groups coexisted. The desire to redraw national boundaries based on ethnic or linguistic lines could lead to tensions and conflicts that challenged the existing political order. Fierce debates over land, resources, and rights emerged, necessitating new political arrangements to manage and address these disputes.

In summary, nationalism threatened the existing political order of the nineteenth century by challenging the legitimacy of multinational empires, calling for self-determination, spreading revolutionary ideologies, and fueling ethnic conflicts and territorial disputes. Its impact was profound, reshaping the political landscape and ultimately leading to the wave of nation-states that emerged in the twentieth century.