Religion has quite frequently been used as an excuse for military motives. Talking specifically about Islam, hadees has been used as a tool to invent excuses for political motivations and military interventions/attacks as and when required.
There has been enormous hue and cry over Ghazwa-tul-Hind for years. This was probably first used by self-styled Jihadi activists in Pakistan for getting public support in Pakistan and raising funds to be used in their attacks in Kashmir with the aim of conquering India and creating what they call dar-ul-Islam. It is very interesting to note that neither Arabs nor the Mujahideen of Afghanistan made use of these ahadees to wage a war against India. Pakistan Army, ISI and the local Jihadis have a monopoly over Ghazwa-tul-Hind for now, although they don’t talk specifically about Green Pakistani Jihadis waging the war.
Islamists and right-wing-military-apologists have fallen to the propaganda of Pakistan Army and ISI when they propagate waging a war against the neighboring country India, finding excuses for ding so through hadees. Zaid Hamid, the mouth-piece of ISI and Pakistan Army has been making use of Ghazwa-tul-Hind (6 hadees in total), promoting hatred against Hindus and war hysteria. These hadees are available here.
Are they authentic ?
- Just a brief look at these will make it clear that none of these five ahadees are found in Sihah-e-Sitta. Two of these appear to be in the collections of ahadees by Imam Nisai but not in Sunan an-Nisai al Sughra, the book considered to be among the Sihah-e-Sitta, the six books considered most reliable by main-stream Muslims.
- The others are not even found in the reliable collections of respected muhadiseen.
- Note that Imam Nisai died in 915. The years of death of other respected muhadiseen to whom Sihah-e-Sitta are attributed to: Imam Bukhari in 870, Imam Muslim in 875, Abu Daud in 888, al-Tirmizi in 892, Imam Malik in 796, Ibn Maja in 886. All of them died before Imam Nisai. It does not make much sense that we have these ahadees being narrated through Imam Nisai but not through any of the other respected muhadiseen who lived before him.
- They are narrated through a single chain. Reported only once through one companion of the Prophet.
- Considering the reward for participating in this war and the importance of it, as these ahadees tell, they should have been narrated by more companions of the Prophet and should have been there in more books of ahadees.
- It is very important to note that none of these are found in any of the collections of ahadees which the Shia Muslims consider authentic. This raises the question if they were invented by the Ummayads/Abbasids considering their expansionist designs? This is also to be noted that Ummayads did reach Sindh, a part of Hind back then.
- One must also note the fact that we don’t have any history report telling us about the use of these ahadees in the past by Muslim rulers or conquerors, even those who did invade India or waged a war on it. If they were respected and authentic ahadees, we should have such history reports.
Fourthly, it must be remembered that it would have been very easy for Muslim conquerors of India in the past, men like Mahmud of Ghazni, Shihabuddin Ghori, Timur, Nadir Shah and so on, to present the hadith about the ghazwat ul-hind and wield it as a weapon to justify their attacks on the country. The corrupt ulema associated with their courts could well have suggested this to them had they wished. However, no such mention is made about this in history books. In the eighteenth century, the well-known Islamic scholar Shah Waliullah of Delhi invited the Afghan warlord Ahmad Shah Abdali to invade India and dispel the Marathas, which he accepted, but yet Shah Waliullah, too, did not use this hadith as a pretext for this. 
What if they are authentic ?
It is also pertinent to examine how some well-known contemporary Indian ulema look at this hadith report.
- Maulana Abdul Hamid Numani, a leading figure of the Jamiat ul-Ulema-i Hind, opines that this hadith was fulfilled at the time of the Four Righteous Caliphs of the Sunnis, soon after the demise of the Prophet Muhammad, when several companions of the Prophet came to India, mainly in order to spread Islam. 
- Mufti Sajid Qasmi, who teaches at the Dar ul-Uloom in Deoband, is also of the same opinion, although he believes that it might also refer to the invasion of Sindh by the Arabs under Muhammad bin Qasim in the eighth century. 
- On the other hand, Maulana Mufti Mushtaq Tijarvi of the Jamaat-i Islami Hind believes that it is possible that this hadith report is not genuine at all and that it might have been fabricated at the time of Muhammad bin Qasims invasion of Sindh in order to justify it. 
- On the other hand, if this hadith report is indeed genuinewhich it might well bein my view, the battle against India that it predicted was fulfilled in the early Islamic period itself, and is not something that will happen in the future. This, in fact, is the opinion of the majority of the ulema, qualified Islamic scholars. And this view accords with reason as well. 
- It is quite likely that the ghazwat ul-hind that this report predicted took the form of the attack by an Arab Muslim force on Thana and Bharuch, in coastal western India , in the 15th year or the Islamic calendar in the reign of the Caliph Umar. 
- Equally possibly, it could have been fulfilled in the form of the missionary efforts of some of the Prophets companions soon after, in the reign of the Caliphs Uthman and Ali, in Sindh and Gujarat .
- Some other ulema consider this hadith to have been fulfilled in the form of the attack and occupation of Sindh by Arab Muslims led by Muhammad bin Qasim in the 93rd year of the Islamic calendar, which then facilitated the spread of Islam in the country. 
- This might well be the case, for the hadith report about the ghazwat ul-hind contained in the Masnad of Ahmad ibn Hanbal, a well-known collection of Hadith narratives attributed to the Prophet, mentions that the Muslim army that would attack India would be sent in the direction of Sindh and Hind. 
Opinion of the religious scholars
I inquired about the authenticity of these ahadees from a few religious scholars and would like to share their opinion in this regard:
Such things exist in the hadith collections, which are often either placed or mounted on a symbolic meaning, or they talk about something historic which has happened in the context of what we believe in self-defense. Further, the hadith in question can be doubted about their autenticity as they are not found in any reliable and agreed upon source. The chain of narrators is weak to be considered authentic.In this day and age what would govern the relations of Muslims and followers of other religions, are the international treaties and covenants that ensure the state security, peace and freedom of belief for all human beings.These treaties are binding on Muslims, especially as they are consistent with the approach of Islam declared in the Qur’an about the obligation to respect the religions and the freedom and security of other peoples.Hence, the use of such hadith for political or military motives is discouraged.The Office of the referenda for Religious AuthorityGrand Ayatollah Mohammed Hussein Fadlallah
assalaam o alaykumI have tried to find out the sources of these traditions. None of these traditions is found in reliable soruces like Bukhari, Muslim, Mu’atta etc. If we suppose them to be reliable they talk about an even that has happened already. They do not talk about Pakistanis fighting Indians. They talk about Arabs on an expedition to India and conquering it.Tariq Mahmood HashmiAssociate Editor
SalaamAll these ahadith refer to troops going from Palestine and Syria and returning to those regions. Even if these ahadith were authentic, and they are indeed found in reliable books, they have nothing to do with any possibility of an Indo-Pak war.The other important thing to note is that Abu Huraira, the companion-narrator is suggesting that it was something that was about to happen during his lifetime. it is quite likely that Muhammad Bin Qasim’s conquest of Sind was being prophesied in these ahadith.
The third important matter to note is that a message as important as the one mentioned in these narratives is described in all different versions through only one companion. Clearly, if the message was important, there should have been several narrators mentioning it.
This message therefore cannot be employed as an excuse to fight against India. We can fight against India or any other nation only if conditions of Jihad are satisfied, which are: it should be declared by a Muslim ruler, Muslims should be at least half as militarily strong as their enemies, and the enemy should be guilty of blatant injustice against a group of people. Any individual or group of people cannot declare Jihad on their own against anyone; if they do, they will be guilty of creating fasaad fil ‘ard (mischief on earth). 
Information on the ahadees available at http://www.ghazwatulhind.com/