press the button
1. To initiate a war with another country, especially a nuclear war. Many fear that the recent decision to restrict the country's access to foreign oil and other imports may drive their leader to press the button.
2. By extension, to initiate or instigate something. After debating it with myself for nearly a year, I decided to press the button and start my own company.
press the button
initiate an action or train of events. informal During the cold war period, this expression was often used with reference to the possible action of the US or Soviet presidents in starting a nuclear war.