Jacobus Andries Diederik Kruger was born on 31 Mei 1871 on the farm Rietvlei in the Potchefstroom district.
In 1891 he joined the State artillery and later in that year he joined the Swaziland mounted police and was a sergeant when the war broke out.
Under General Chris Botha that was the commandant of the Swaziland mounted police, he took part in the battles of Colensoe, Bosrand, Peters Hill, Helpmekaar, Scheepersnek, Allemansnek, Spieshoek, Talene, Melmoth and some other small battles.
He was promoted from second lieutenant to First Lieutenant in August 1901 and after the battle of Talene to Commandant of the Swaziland commando.
He was seriously wounded a few time but stayed in the veld till the end of the war.