[Tried to answer this question when it was posted on English Language and Usage but the question was locked there even as I was editing the quotation, and subsequently migrated here. Rather than waste the time I spent finding an example that shows clearly the style of writing where this construction was used, I'm replying here on ELL.]
Yes, that is an alternate form of conditional statement that doesn't rely on if. But starting a conditional sentence with a modal verb in that manner is rather old-fashioned, as this example shows:
We did not then know that this movement was but the opening of the siege of Port Hudson, in which the One Hundred and Sixteenth was destined to play as important a part as the men we envied, and that while Emory's Division could inscribe on their battle flags "Fort Bisland," and Grover's Division "Irish Bend," Augur's Division would soon be enabled to inscribe on theirs "Plain Store." Could we have foreseen it, we should have been better contented with our seemingly unfortunate lot. [my emphasis]
—The One Hundred and Sixteenth Regiment of New York State Volunteers: Being a Complete History of Its Organization and of Its Nearly Three Years of Active Service in the Great Rebellion. To which is Appended Memorial Sketches and a Muster Roll of the Regiment, Containing the Name of Every Man Connected with it By Orton S. Clark, 1868
P.S. "Had we known at the time..." or "Had we been able to foresee..." are still in mainstream use in the 21st century.