Havoc is a funny old word. I think that I only use it myself in the phrase play havoc, as in "Ortolan plays havoc with my digestion". This is because I never realised that havoc is, technically, a military command.
There are two bits, you see, to being a soldier. There are the battles, which are rather difficult and require discipline. Then, when the battle is won and there are only civilians left, the soldier's fun really starts.
So once the general is happy that the enemy has been routed and the city is ours he gives the order to his men that they may plunder, pillage and ransack everything that isn't bolted down and some things that are. This order is Havoc, because havoc literally means plunder. And once the general has cried havoc the troops can do whatsoever and whomsoever they like.
Once you realise that crying havoc was a standard part of warfare and, indeed, goes straight back to the French crier havoc, Mark Antony's promise to Julius Caesar's corpse makes a lot more sense:
Blood and destruction shall be so in use
And dreadful objects so familiar
That mothers shall but smile when they behold
Their infants quarter'd with the hands of war;
All pity choked with custom of fell deeds:
And Caesar's spirit, ranging for revenge,
With Ate by his side come hot from hell,
Shall in these confines with a monarch's voice
Cry 'Havoc,' and let slip the dogs of war;
That this foul deed shall smell above the earth
With carrion men, groaning for burial.
Ate, by the way, was a goddess who personified a mad impulse towards destruction. She was the eldest daughter of Zeus, and I fear I may have gone out with her at some point.
Anyway, what this post is leading round to, is that "Cry 'Havoc' and let slip the dogs of war" is, technically, a booty call.
The party was a mixed success