The revolutions of 1830 showed the flexibility of the system. The new French regime was accepted, with Palmerston leading the way. The British doctrine that the territorial status quo, and not the domestic regime, mattered was accepted by the other powers. But the revolt in Belgium in the same year against William I, king of the Netherlands, showed that even the territorial status quo could alter. His appeals to the sanctity of the 1815 treaties went unheeded, an illustration of the primacy of power over law in international relations, and the vulnerability of small states in nineteenth century diplomacy. Belgium’s creation in 1831, bolstered by a guarantee of its neutrality by the great powers, was the destruction of one state (the Netherlands), as much as the formation of a new one. Belgian security was only important to the great powers because they feared that the Belgian revolutionaries might unite with France, damaging the territorial buffers of 1815. If the Concert of Europe was sufficiently flexible to accommodate Belgian independence, the new state proved a model of restraint, eschewing any aspirations towards union with France which would have meant war. Belgian independence was preserved by the constellations of great power politics, rather than the flimsy treaty guarantees of 1831 to which no great power felt bound.
Security concerns rather than ideological principles had dictated the policy of the three eastern and conservative great powers. Austria’s and Russia’s repression of revolts in Italy in 1830 and Poland in 1831 respectively showed that the spheres of influence marked out in 1815 were broadly respected. Prussia also fulfilled its role as guardian of the Rhineland against any possible French invasion in 1830, underlining the geopolitical shift of its priorities towards western Germany, which had taken place in 1815. The German Confederation could not play the defensive role assigned to it by the 1815 settlement. Military mobilization was dependent on the initiative of individual states, most notably Prussia. That state confirmed itself as the leading German power, while Austria had non-German commitments in Italy. The Third Germany looked to Prussia for protection against the potential French menace – the rights enshrined in treaties still depended on military force. It remained a balance of power system, not an equilibrium of rights and interests. Restraint was induced by calculations of power, spheres of influence, and grouping rather than an automatic respect for international treaties.
The 1830 revolutions appeared at first glance to have opened an ideological rift within Europe with three conservative eastern great powers facing liberal France and Britain. In 1833 Austria, Prussia, and Russia concluded a treaty allowing intervention in aid of any legitimate ruler against revolution. In 1834 France, Britain, Spain, and Portugal concluded the Quadruple Alliance.
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The 1848 revolutions represented a massive challenge to the territorial settlement of 1815, particularly in Central Europe where the formation of German, Hungarian, and Italian states became possible. The Concert of Europe demonstrated its continued strength in preventing any territorial change and averting a war between the great powers. This was partly due to the monarchical solidarity of the three eastern powers, though calculations of power relations played the decisive role. For the most part, the habits of grouping and restraint informed the foreign policies of the great powers, despite nationalist pressures. Small states, such as Piedmont-Sardinia in Italy, which challenged the territorial order were left to pay the price, while those, like Belgium and Denmark, which sought the maintenance of the status quo were supported. The incentives during the international crisis were for restraint. Yet there was also evidence of flexibility. Statesmen were willing to countenance change – such as the unification of Germany under Prussia – as long as it did not disrupt the balance of power. To this extent, the Concert system survived 1848 in terms of the principles of the behavior of the great powers.
Britain and Russia played a particularly important role in controlling the international consequences of the revolutions in their particular spheres of influence. Britain recognized another new French regime which signaled its conservative foreign policy by assuring Spain and Belgium of its peaceful intentions. Russia played a much more dramatic role in Central Europe where it suppressed a Hungarian revolt which threatened the Habsburg Empire. Austria was active in Italy, defeating Piedmont- Sardinia in 1848 and 1849.