For some 200 years (1400-1200 BC) the Hittites had a secret regarding the making of iron. It wasn't smelting, since that was already known to the Chinese and others. And it wasn't the making of steel, because steel is just iron containing carbon, and iron had to contain carbon at that time anyway in order for it to be smeltable at the temperatures that could then be attained. Was the secret the process of repeated hammering and quenching? The reason I ask is because I am taking up the question in a book I am writing.

According to Why Things Break, a recent book by materials chemist Max Eberhart, hammering and quenching is indeed part of the secret to making steel hard.

If I remember the book correctly, large crystals make a material more flexible, while small ones make it harder. When a hot piece of metal is cooled, slower cooling produces larger crystals. Japanese swordmakers went so far as to coat part of the hot blade with clay before quenching--keeping the center supple while the edge was hardened. (Hard materials can take and keep sharper edges.)

Hot hammering encourages the metal to reform its crystal structure; quenching then reforms it as small grains for a harder surface. The center would cool more slowly, keeping the blade supple.

Here's a website devoted to Toledo swords that tells something of how the Toledo forging process works.