[Mickeeezy]

from what i saw in the anime, isshin is strong as DUCK ! and kills the grandfisher in one simple swing.
isshin even said "all captain ranked shinigami's control the size of their zanpktou. otherwise they would be swinging around a skyscraper-like sword."
so im guessing he was a captain.

but what i dont understand is. why didnt Kon or the Trio's tell ichigo that his dad is a shinigami. or why isshin never appeared again as a shinigami. WHACKK !!!
so sad.

edit: i dont know if its true but i also heard ichigo's mother was a quincy.