In The Name of Allah, The Most Merciful, The Bestower of Mercy.
Allah [The Exalted] said:
لَقَدۡ أَرۡسَلۡنَا رُسُلَنَا بِٱلۡبَيِّنَـٰتِ وَأَنزَلۡنَا مَعَهُمُ ٱلۡكِتَـٰبَ وَٱلۡمِيزَانَ لِيَقُومَ ٱلنَّاسُ بِٱلۡقِسۡطِۖ وَأَنزَلۡنَا ٱلۡحَدِيدَ فِيهِ بَأۡسٌ۬ شَدِيدٌ۬ وَمَنَـٰفِعُ لِلنَّاسِ وَلِيَعۡلَمَ ٱللَّهُ مَن يَنصُرُهُ ۥ وَرُسُلَهُ ۥ بِٱلۡغَيۡبِۚ إِنَّ ٱللَّهَ قَوِىٌّ عَزِيزٌ۬
Indeed We have sent Our Messengers with clear proofs and revealed with them the Scripture and the Balance (justice) that mankind may keep up justice. And We brought forth iron wherein is mighty power (in matters of war), as well as many benefits for mankind, that Allah may test who it is that will help Him (His religion), and His Messengers in the unseen. Verily, Allah is All-Strong, All-Mighty. [Surah Al-Hadeed. Verse 25]
Imaam As-Sadi [may Allah have mercy upon him] said: Allah informs us that He sent the Messengers to guide the creation (humankind and Jinn) and that He supported them with clear evidence that manifests the realities, demonstrates the truthfulness of the Messengers and the reality of what they brought. He revealed to them the Scripture, which contains guidance and mercy, as well as the Balance, which is justice, through which justice, its foundation, and subsidiary branches are known, and so that humankind may maintain justice when they act on it in their beliefs, manners, deeds, behaviour, and all their affairs. As a result, when they act on what Allah revealed in the Scripture and the Balance, all their dealings and circumstances will be founded on righteousness and steadfastness.
And Allah informs us that He sent down iron, which has great power in matters of war as well as many advantages for humanity. He stated its advantages explicitly in terms of benefits in matters of war and then generally in terms of all other matters. Allah sent down iron for these helpful, necessary matters and affairs that bring about perfection, both specifically and in general. Except for a few things, everything needs iron. Allah mentioned it in the context of the favours He has bestowed upon the servants, which makes it necessary for these favours to be extracted in every way, necessitating further the necessity of education in military expertise and war affairs, the manufacture of weapons and their accessories, maritime transport, land transportation, aircraft, and other things that aid the servants in their religious and worldly affairs.
وَأ عدوا لهم ما استطعتم من قوة ومن رباط الخيل ترهبون به عدو هللا وعدوكم
And make ready against them all you can of power, including steeds of war (tanks, planes, missiles, artillery, etc.) to threaten the enemy of Allah and your enemy]. [Surah Al-Anfaal. Ayah 60]
Take every precaution for yourselves.
[Surah An-Nisaa. Ayah 102]
This addresses the issue of preparing for as much power as is feasible, including doing so mentally, politically, monetarily, and religiously, as well as taking all necessary precautions against the enemy. This generality includes all types of crafts—small and large—as well as innovations and fortifications for defence. As a result, this Islamic faith encourages healthy advancement and strength in all respects, in contrast to the false claims made by its foes that it is weak, careless, and worn out. (1) [End of quote]
Finally, the preparation of weapons is the task of Muslim governments, not insurgent organisations. The Khawaarij (ISIS and their ilk) have no authority; instead, they are bandits, innovators in religious affairs, and terrorists. Upright Muslims obey their rulers in good, fulfil the agreements their rulers have established between their nations and other nations, and uphold upright conduct whether in their home countries or abroad. Must-read articles by Shaikh Abu Khadeejah and Shaikh Abu Iyaad [may Allah protect them].
The Protection of the Blood, Wealth, and Honour of Non-Muslim Citizens in the Islamic Shariah
Al-Allaamah Salih Aal Ash-Shaikh: Shariah Calls for Protection of Life and Property
Al-Allaamah Salih Al-Fawzan: The Islamic Shariah Provides Security for Muslims and Non-Muslims and Those Who Violate It Are Kharijites Who Are to Be Fought and Severely Punished
The Islamic Shariah on the Foundation of Muslim Relations With Non-Muslims Who Do Not Show Aggression and Hostility
Islam and the Muslims Are Free and Innocent of the Kharijite Extremists and the Islamic Shariah Has Come With a Command to Fight Them
Al-Allaamah Saleh Fawzaan on Jihaad in our times and the guidelines of Jihaad according to Islam – Abu Khadeejah : أبو خديجة
The Prophet of Islam would not kill diplomats, ambassadors, emissaries or foreign delegations even if they were sent by the worst of his enemies
Ref 1: Ad-Dalaa’il Al-Qur’aaniyyah Fee Annal Uloom Wal-A’maal An-Naafi’ah Al-Asriyyah Daakhilatun Fid-Deen Al-Islaamiy. pages 9-10