Why does it always return true?

Beginner question, sorry if it's not the right place to ask Trying to learn how logic works in JS, can't figure this out

if (firstSymbol === "A" || "a" || "D" || "d") {
    if (secondSymbol === "z") {
        alert("It does!"); 
        break;
    }
}

I expect it to say "It does!" and break in case if the firstSymbol is A, a, D or d AND the secondSymbol is z , but for some reason it says "It does!" and breaks regardless of what the firstSymbol is and only checks if the secondSymbol is z.