Menno van Coehoorn, copy after Caspar Netscher. After the disasters of 1672 more attention was paid to the nation's defences. Baron Menno van Coehoorn (1641-1702) enjoyed an international reputation as an expert on fortifications. He received an academic education in mathematics and fortifications, then a subject taught at universities. In the late 17th century Menno van Coehoorn began work on a defensive line designed to keep the enemy in check the Republic's frontiers.