Maximilian Robespierre was the leader who was convicted by the court in July 1794, arrested, and sent to the guillotine. Robespierre was a prominent figure during the French Revolution and played a significant role in the Reign of Terror.

Background:
- Maximilian Robespierre was a lawyer by profession and a member of the Jacobin political club.
- He strongly advocated for radical political and social reforms and was one of the key leaders of the Committee of Public Safety, which held executive power during the French Revolution.
- Robespierre was known for his uncompromising stance on revolutionary ideals and his belief in creating a virtuous republic.

The Reign of Terror:
- The Reign of Terror was a period during the French Revolution characterized by mass executions and suppression of political opponents.
- Robespierre and his committee were responsible for implementing policies that aimed to eliminate counter-revolutionaries and maintain control over the revolution.

Conviction and Arrest:
- However, as the Reign of Terror continued, Robespierre's power and influence began to decline.
- He became increasingly unpopular due to his radical policies and the indiscriminate use of the guillotine.
- Robespierre's enemies within the National Convention, the governing body of France at the time, saw an opportunity to remove him from power.
- On 27th July 1794, Robespierre and his supporters were declared outlaws by the Convention, effectively making him an enemy of the state.

The Guillotine:
- The guillotine was a device used for capital punishment during the French Revolution.
- It was a symbol of the revolutionary government's power and was employed to execute thousands of people, including King Louis XVI and Queen Marie Antoinette.

Execution:
- After being declared an outlaw, Robespierre was arrested along with his followers.
- On 28th July 1794, they were brought before the Revolutionary Tribunal and quickly convicted of various crimes.
- The following day, on 29th July, Robespierre and 21 of his associates were executed by guillotine in the Place de la Revolution in Paris.
- Robespierre's execution marked the end of the Reign of Terror and the decline of the radical phase of the French Revolution.

In conclusion, Maximilian Robespierre, the leader of the Committee of Public Safety and a key figure in the French Revolution, was convicted, arrested, and executed by guillotine in July 1794. His radical policies and the widespread use of the guillotine during the Reign of Terror contributed to his downfall.