From Longman Dictionary of Contemporary Englishshow your handshow your handINTENDto make your true power or intentions clear, especially after you have been keeping them secret There were so many rumours that the company was forced to show its hand. → show
Examples from the Corpus
show your hand• At Michaelmas 1183 Henry showed his hand.• For one thing he needed hard evidence, and to get it he would have to show his hand.• Not the time to show our hand.• Now the government has shown its hand.• Kingfisher was forced to show its hand after rumours that a bid was in the offing began to circulate on Tuesday.• He said that he wouldn't be bullied into showing his hand first.• Though nobody on the government side had shown his hand, it was hardly necessary.• When Dastmalchi called and showed his hand, Tom knew the game was up. 