Complex sentence: The last attempt to torpedo the peace process occurred on August 19, when Pulikovsky suddenly issued an ultimatum to the rebels to leave Grozny within 48 hours-in the event of non-compliance, attacks would be launched from all directions and with all available means.
Split into simpler sentences: The last attempt to torpedo the peace process occurred on August 19. On that day, General Pulikovsky suddenly issued an ultimatum to the rebels to leave Grozny within 48 hours-in the event of non-compliance, attacks would be launched from all directions and with all available means.