Castle towers, the symbolic representation of the respective castles, are said to have been brought into existence by Nobunaga ODA, and reached the peak of their popularity around the Battle of Sekigahara, but as the number of castles decreased with implementation of the Ikkoku Ichijo Rei (Law of One Castle per Province) by the Edo bakufu (Japanese feudal government headed by a shogun), a ban was also imposed on construction of new castles and extension and reconstruction of the existing castles according to Buke shohatto(Acts for the Military Houses).
織田信長に始まったともいわれる城の象徴である天守は、関ヶ原の合戦前後に築城の最盛期を迎えるが、江戸幕府の一国一城令による破却で城郭の数は減少するとともに、武家諸法度により新たな築城や増改築は禁止された。