The Antigonid kingdom of Macedon's cavalry only constituted a small fraction of the army. Duncan Head estimates this fraction as between 5 and 10% of the total strength of the Antigonid armies. This may well be due to over-campaigning, high casualties or even because many of the Macedonian noblemen who formed much of the heavy cavalry of Philip II and Alexander went east and never came back. But, by the time of Philip V and Perseus, cavalry strength had slowly increased. Philip V had a cavalry force of 400 'Household' cavalry, called the Royal or Sacred Ile in a campaign in 219 BC. This small number of native horse was then supplemented by mercenary cavalry.