The Chafetz Chaim zt"l writes in his commentary on the Nach, "At the end of the exile which we are entering into right now, there will be an awesome war between the sides of Holiness and Impurity, and the side of Impurity will cast down mighty arrows… There will not remain from this war people who are completely intact with all of their limbs except for a very few. These will be the remnants of whom Hashem will call upon; these will be the true mighty ones and the true masters of the Torah… Each one according to his level and according to the amount of urging he gives to others that they should perform their duties with faith." (Taken from the sefer Vehaer Einenu)
Rav Eliyahu Lopian zt"l added the following explanation to the above words, "In any battle, when the final outcome approaches of who is to be the victor and who is to be the looser, both sides put forth their greatest effort with all the strength they have left in them. So too it is here at the end of this exile as we are approaching the deciding moments, that the side of Impurity - the evil empire knows that it is only moments away from being completely annihilated from existence. Therefore, it is emboldening itself with all of its power to dispose of Yisrael (G-d forbid) and to distance them from Hashem blessed be He." (Lev Eliyahu vol. 2 pg. 112)
It is clear from the above two quotes that the main war we will face in the end of days will be against the forces of Impurity, and that that the side of Impurity will be attacking with very mighty and powerful attacks against those few who are fighting to stay strong and connected to G-d. We only need to look outside in the street to see that the battle is well under way, and almost all the fences of holiness, purity and modesty have been destroyed.
The prophets make many references to the battle with the 70 Nations that will take place in Jerusalem in the End of Days. Based on the above, we can suggest that this is not referring to a physical war with each of the 70 nations arriving to Jerusalem with their different flags and uniforms, but perhaps it is referring to a spiritual war in which the influences of the 70 Nations will come to Jerusalem with the goal of attacking our Holiness. Let's take a look at what Rebbe Nachman has to say about the 70 Nations in Likkutei Etzot Brit #10:
The desire of niuf (immoral sexual desire) is the all inclusive evil, in which all of the evil of all of the 70 Nations are included in. For each Nation has a hold in its own specific type of evil, that is, some specific bad trait or evil desire that is unique to that Nation. However, the desire for niuf is the all inclusive evil, and in it is gathered and included each and every single evil from each and every single Nation. It contains all the bad of all the desires, and in it burns all the bad of all the desires as one large inferno. This inferno is what burns inside of a person when he feels the desire for niuf.
However Hashem has separated us from all of the Nations, and He has exalted us above all of the tongues (languages). Therefore, we must separate ourselves from all of their evil, that is, from all of their desires which have no connection to us whatsoever, specifically from the desire of niuf which is the all inclusive evil of all the Nations as mentioned above. For this is the main difference and distinguishing between us and the Nations, that we separate ourselves from niuf, for this is the main holiness of Yisrael. For it is within a persons' power to remove his thoughts from this desire and destroy it completely; and this is our main holiness.
The words of the Chafetz Chaim seem very clear now and we are certainly in a fierce battle with the 70 Nations at this very moment, specifically in the area of holiness. Furthermore, the Prophet Isaiah makes reference to this idea when he describes the survivors who will remain in the End of Days, "Of every remnant that will be in Zion and every remaining one in Jerusalem, 'Holy' will be said of him (Isaiah 4:3)." And, "There will be a path and a road there; it will be called 'The Path of Holiness,' and no impure person will traverse it… The redeemed will walk there (Isaiah 35:8-9)"
May Hashem give us all the strength to merit walking on the Path of Holiness, amen.