Hello, 

Let me start by what are all the defence exams that you can apply for:

NDA & NA Exam

• The exam is conducted by UPSC twice every year.
• Students who are studying in the 12th standard or completed the same are eligible to apply for this exam, provided they fulfil the complete eligibility criteria.
• The NDA Exam comprises of 2 stages an offline test and SSB Interview.

CDS Exam

• Graduates or the candidates in the final year of graduation can apply for the CDS exam, provided they fulfil the requisite eligibility details, as specified in the official notification. Women candidates can apply for OTA only.

AFCAT Exam

• AFCAT exam is conducted for recruitment in:
• (a) Flying Branch
• (b) Ground Duty (Technical) Branch
• (c) Ground Duty (Non-Technical) Branch
• Candidates who possess a graduation degree can apply for the AFCAT exam, provided they meet the complete eligibility requirements.

Indian Coast Guard

Central Armed Police Forces

• The UPSC CAPF Assistant Commandant exam is conducted for recruitment to the following paramilitary forces:
• (a) Border Security Force (BSF)
• (b) Central Industrial Security Force (CISF)
• (c) Central Reserve Police Force (CRPF)
• (d) Indo Tibetan Border Police (ITBP)
• Sashastra Seema Bal (SSB)

Indian Air Force (Group X & Y)

These are the major Defence Exam conducted in India, which provide a opportunities to numerous aspirants of the country to join the Armed Forces and serve the nation

For more detailed information  please go through the following links. 

https://www.google.co.in/amp/s/gradeup.co/defence-exams-in-india-i_amp

https://www.toppersexam.com/DEFENCE-EXAMS.html

Hope this helps you ....