it depends on which northern campaign.
the first was 2 prong attack. 219AD liubei attacked hanzhong and won. guanyu attacking jingzhou and won. but guanyu attacked and steal food supplies from wu becos he cant support his bloated troops after the wei troops surrendered and went under his command. subsequently he lost to wu later and got killed.
the second stage was led by ZGL. he organised 5 campaigns.
the third stage was the series of campaigns led by jiangwei from 238AD onwards. 11 campaigns, and it drained shu of manpower and reasources cos mostly not well planned.
When I talked about 诸葛亮北伐，it means zhu ge liang is the general, not 刘备or 关羽.
The strategy can only work if they attack from 荆州and益州together.
Attacked from 益州alone is darn difficult. Not to mention 司马懿is equally good and leading a bigger army.
Zhu ge liang 六出祁山。
The first time was the one has the highest chance to success but they blew it up.
Only if they manage to capture 长安and虎牢关，and hold there, then only they have a chance to go inside 中原。
But 虎牢关is darn hard to conquer. They cannot afford to bypass it, coz once they bypassed it, they will be chopped half by 魏。so many times 北伐，zhugeliang is no where near 长安or 虎牢关，司马懿was just sitting there, relax and waited for 诸葛亮to finish food supplyIt is saddening for all 诸葛亮fans, but this is the truth.
荆州side, 襄阳is a stronghold, don think anybody manage to take it from 魏after they got it from 刘表。you do know that 襄阳is the city that hold Mongolian army for decades during 宋朝right?
