Parliament's main strength was that the Navy supported them. This meant that they gained access to soldiers and supplies from overseas. They also gained a lot of money from this, as the Navy were very rich and powerful.They could also send soldiers to places were there were battles by boat, instead of on foot and this helped because the soldiers wouldn't tire on the journey, and it was much quicker. Furthermore, they could quickly get reinforcements by boat, if the Royalists proved too strong for them.