Related Clues:

• 'This is only ___ . . .'
• Trial blast that produces a mushroom cloud
• A-bomb trial
• Bikini atoll event
• Protested event, briefly
• Explosive trial, briefly
• Defense initiative, for short
• Military trial, briefly
• Protested event, for short
• Provocative military move, briefly
• "This is only ___"
• Alamogordo experiment
• Cause of an intl. incident, maybe
• Big bomb trial, briefly
• Weapons check, in brief