Were there many authorities who held that the oaths prohibit only a military takeover of the land?

Hello Rabbi, on the question of whether the oath not to “go up as a wall” means only with a fight, or even peaceful immigration, the Avnei Nezer and Rabbi Chaim Palagi (the first responsa to be written on the matter) both hold that it means only with a fight, but peaceful immigration is allowed, as you quote in your book.

I would like to ask you whether you would agree the following sources below all hold the same opinion: 

1. The Kaftor Vaferach
2. The Maharsha
3. The Megillas Esther
4. The Noda Beyehuda
5. The Ahavas Yonasan in Shoftim
6. Rabbi Yaakov Emden

These sources all mention conquering the land as the violation of the oaths, so doesn’t that imply that they hold the immigration with permission from the nations is allowed?

Yes, you’re correct that those poskim held that only conquest is forbidden, not massive peaceful immigration.  Regarding the Avnei Nezer, as I explain on page 213 of my book, he later conceded that mass immigration, even without war, is forbidden. He at first suggests that it would be allowed but then retracts that position due to the Gemara in Yuma 9b. The case where the Avnei Nezer permits mass immigration is when the ruling power gives permission for all Jews to come, a very unlikely scenario that hasn’t happened since the time of Cyrus.

Even the authorities you mentioned would agree that founding a state peacefully would be a violation of the oath against forcing the end of exile. In any case, the current state was not founded peacefully, so this is an academic point.