When Can You Lead a Spade? Understanding "Breaking Spades"

The Rule of the First Cut

You cannot lead a Spade as the first card of a book until a Spade has been played previously to "cut" another suit. This is known as "breaking" the suit.

The "Spades Only" Exception

If it is your turn to lead and the only cards left in your hand are Spades, you may lead a Spade even if they haven't been broken yet.