Complex sentence: General Botha observed that the strung out column provided an ideal opportunity for an overwhelming force to roll up the isolated and spread out groups of commonwealth troops piecemeal and immediately ordered a large Boer force of mounted men to attack the small isolated rear guard of the column.
Split into simpler sentences: General Botha observed that the strung out column provided an ideal opportunity to be attacked by an overwhelming force which could roll up the isolated groups of commonwealth troops piecemeal. Botha ordered a large Boer force of mounted men to attack the small isolated rear guard of the column.