About Masugata
  I would like to expalain the structure of Masugata, taking the most simple example.
  People built a set of banks covered with stone-walls in front of the town, to prevent distruction by the enemy, in the way the picture displays.
  The shape of arrangement is 《 「  」 》 to set them facing each other across the way. Then they built , next to Masugata, the walls, banks, row of houses, or so.
  In such a situation, the marching soldiers of enemy could enter the town only after turning at right angle twice. It would take much time.
  Building Masugatas at every main stage-towns along main Kaidos, The army antagonizing Shogunate would exhaust much quite time to reach Edo or the strategically important cities.
  Meantime, Shogunate government could make good ready for the battle.

Formula of Masugata

Masugata-koguchi in the Early Modern Age

cited from：小学館, 『ビジュアル・ワイド　日本名城百選』2012年
  In Japanese Masu means a Square vessel and Gata (kata) means a form or a shape.
  To make marching course turn at a right angle twice, it's not always the shape 《 「  》. Other shapes of banks or walls would better stand against marching on straight.
  The steep of the mountain or the strong houses would play the same role. It needs the constructions hindering the enemy marching.