You want an army of giants, so what do you do? Breed tall people, of course - but don't forget to treat them like crap.
"The Potsdam Giants was the name given to Prussian infantry regiment No 6. The regiment was composed of taller-than-average soldiers, and was founded in 1675. It was eventually dissolved in 1806, after the Prussians were defeated by Napoleon. Throughout the reign of the Prussian king Friedrich Wilhelm I of Prussia (1688–1740), the unit was known as the "Potsdamer Riesengarde" ("giant guard of Potsdam") in German, but the Prussian population quickly nicknamed them the Lange Kerle ("long fellows")."