Why did Garibaldi stop short of marching on Rome in 1860?

Giuseppe Garibaldi’s march on Rome in 1860 was halted primarily due to intense political maneuvering and the fear of international intervention. While Garibaldi was committed to making Rome the capital of a unified Italy, his ambitions conflicted with the cautious diplomacy of the Piedmontese government.12

Several key factors prevented his advance:

• French Intervention: Rome was defended by a French garrison, and it was feared that an attack on the city would provoke a military response from France.12
• Piedmontese Control: Count Cavour, the prime minister of Piedmont, feared that the Risorgimento was becoming a radical popular movement led by Garibaldi’s followers rather than the monarchy. To maintain control over the unification process, Cavour ordered Piedmontese troops to invade the Papal States, effectively intercepting Garibaldi and pressuring him to yield his conquests.123
• Political Stability: King Victor Emmanuel II and his government viewed Garibaldi’s radical, anticlerical leanings as dangerous. There was also concern that Garibaldi’s immense popularity eclipsed that of the king, and that he might be swayed by republican influences to abandon the monarchical cause.2

Ultimately, Garibaldi relinquished his dictatorship and retired to Caprera to ensure the success of a unified Italy under the king.12