sentences:  Plans for the fortifications were prepared by Lieutenant-Colonel Augustin Ehrensvärd, who was also tasked with constructing the fortresses in 1747.Construction started in 1748 and continued with increasing tempo as the external political situation deteriorated in 1749 and 1750.Over half of the Swedish army in Finland was tasked with the construction and in 1750 more than 6,000 men were working on the fortifications at Svartholm and Sveaborg.