Electronic Warfare – The untold story of 1971

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As a young Flight Lieutenant with an electronic eavesdropping unit of the Indian Air Force, (Wing Commander) M L Bala writes about the unsung role his unit played in hastening the end of the 1971 war.

 As a young Flight Lieutenant with an electronic eavesdropping unit of the Indian Air Force, (Wing Commander) M L Bala writes about the unsung role his unit played in hastening the end of the 1971 war.



It is now more than 40 years when India fought a decisive war with Pakistan in the year 1971 and a new nation by the name of Bangladesh was created by partitioning of the then Pakistan, which itself was created by the British by partitioning India in 1947 on the infamous two-nation theory. Many articles and books have been written about this war by war historians, political leaders and the soldiers who might or might not have fought this war themselves. I have gone through most of these books, articles and the contents published on the Internet. Very vivid and interesting accounts have been written in these publications. However, I have not come across any account which I shall be giving in this article. This is an account from a person who has proactively fought this war. Hence, it is an account in the first person by an air force officer who himself was directly involved in this episode –

I was posted to a Signals Intelligence Unit in the year 1970, after completing a Refreshers Course at the Air Force Technical College at Bangalore. I was a Flight Lieutenant in the Indian Air Force and belonged to the then Technical Signals Branch. I had joined the Indian Air Force in the year 1963 after completing my doctorate degree in Physics from Allahabad University, and declining the post-doctorate fellowship from the University of Pensylvennia, USA. The reason for my declining the post -doctorate fellowship was that I wanted to serve my country proactively, after China attacked India in the year 1962. In fact, as I understand, I was the first D Phil (only Allahabad & Oxford University call it D.Phil, all other Universities call it PhD) to have joined the technical branch of the Indian Air Force. I believe I still hold this record although many air force officers have completed their Doctorate while serving the air force, army or navy.

My new Unit was called a Wireless Experimental Unit (WEU) . It was commanded by Squadron Leader ON Kapoor of the same branch. He was known as the OC of the Unit. There were four other officers of Technical Signals branch and one officer of the Administration branch in the Unit. Being the second senior most officer in the Unit , I was also called the 2 I/C of the Unit.

The Unit was working under the Signals Intelligence Directorate (S.I.Dte) of the Army Headquarters, which was an Inter-service organisation . I was, therefore, summoned by Brigadier Juneja,the Director of the S I Dte for briefings, along with my OC. It was there that I understood that, though working under the Army Headquarter, it was an Inter service Directorate. There were two Deputy Directors-one each from air force and navy. Further, there were three Assistant Directors -one each from army, navy and air force. Wg. Cdr. A K Bannerjee (popularly known as ‘Benjo’) was the Assistant Director Signals Intelligence (Air) , in short ADSI (Air)at the SI Dte.

The Directorate had several WEUs for army, navy and air force all over India. The role of the Directorate, as the name suggested, was to gather Signal Intelligence (SIGINT) of the neighboring countries like Pakistan, China, Burma, Sri Lanka and other South Asian countries with these WEUs. The task of the Directorate was to monitor the Radio Telephone (R/T) conversations of the neighbouring countries using High Frequency (HF),Very High Frequency (VHF) and Ultra High Frequency (UHF) bands of communication through these WEUs, after intercepting their R/T conversations, The Units endeavoured to monitor them 100% and record the conversations on an audio tape recorder (which were spool type). The task appeared to be simple. But it needed real good patience of the crew manning the Radio Receivers. For HF monitoring, Racal 17 and AR 88 Receivers were allotted to the WEU where I was posted. The task was further complicated due to the following reasons:

Some of the conversations were in languages other than English or Hindi. For example, some languages used were Bengali, Urdu, Pushto used by West Pakistanis, Sindhi, Chinese, Burmese, Jhangi (a local dialect of South-West Pakistani soldiers. Strategic conversations were mostly encrypted at the transmission end, so at reception end,they were garbled and could not be normally understood and the important conversations were of very short duration. 

The task of the R/T Operator manning the radio receiver was:

  1. To carry out searching the various frequencies on the Receivers 24 hours a day,7 days a week,
  2. To log all the monitored conversations ,
  3. To assess the importance of a conversation,
  4. To immediately decode the encrypted conversation by inserting the proper decode card in the Receiver, if the conversation was an encrypted one,
  5. To record the important conversation on the spools of the audio tape recorder provided for the purpose,
  6. To inform the Section Commander, who was normally a Flight Sergeant (now called Junior Warrant Officer ) or a Warrant Officer.

Since it was a very strenuous & painstaking job, which required complete dedication, the tenure of duty of each R/T Operator on the Receiver was kept as 4 hours only, along with a stand-by -duty of another 4 hours, during which he was asked to relieve the R/T Operator on the Receiver after 2 consecutive hours each. The personnel management of these R/T Operator was indeed quite a complicated job, because the humane and the psychological problems of these workers were to be also taken care.


Besides being the 2 I/C of the Unit, I was entrusted the responsibility of the Operations Officer (Ops Officer) of the Unit. In fact, I was posted to the WEU against this vacancy. The Ops Officer of a WEU was not like the Ops Officer of a normal flying station. He had a very sensitive and complicated job to perform. The Unit, being a classified monitoring one, the Ops Officer of a WEU had to handle a lot many ‘Top Secret’ documents. It was the total responsibility of the Ops Officer to peruse each logging carefully and take decision as to which conversation is to be reported to the ADSI. It was his responsibility to ensure the safe custody of the ‘Decode Cards’, and train the R/T operator to use them so that he is able to decode the conversation immediately lest no part of the conversation is lost. It was also his responsibility to handle and maintain all the classified publications/documents held in the Unit.

Beside these important responsibilities, I personally made efforts to develop some ‘Decoding Cards’ myself with the help of one of my junior officers and a technically sound Flight Radio Mechanic non commissioned officer. Of course, I kept my OC informed of my venture, but requested him to keep it to himself, since I myself, was not very sure of the success of my project. I thought of such a project because I had a research background and wanted to make use of it in my duties. I did receive some small success in making a decoding circuit through a Delay Line circuit. However, I never thought of using it during real operations.


After my briefing at the SI Dte, I started getting ready for my duties. I studied the complete theory of the radio receivers being used for the monitoring of the conversations. These were HF and MF radio receivers AR 88 and RACAL RA 17 and used valve (vacuum tubes) in their circuits (Semiconductors & Ics were yet to be seen in military scenario). Being valve radios, which was the technology available to us at that time, they used to get heated up very soon. It was, therefore important to cool them for proper functioning.

The main role of my WEU was to monitor & intercept H F R/T conversations between East & West Pakistan. The political scene in Pakistan was getting heated up by the end of the year 1970 and so was the task of my Unit. There were lot of imbalances between East & West Pakistan. Though both the parts followed the same religion, there was vast difference in their culture, life-style and language.

The main political party in East Pakistan-the Awami League, led by the dynamic leader, Sheikh Mujib-ur-Rahman resented the measures being forced on them by the Punjabi-backed national government. Sheikh Mujib was earlier arrested in the year 1968.By the end of 1970,President Ayub Khan was replaced by General Yahya Khan. During the general elections of Pakistan in December, 1970, Awami League of East Pakistan won by a huge majority. In fact they swept the poll.They captured 298 out of 310 seats in East Pakistan and 167 seats in the national Parliament. Sheikh Mujib claimed to lead the government which was rejected. Opening of Parliament was indefinitely postponed on 1st March, 1971. A general strike was called in East Pakistan on 2nd March 1971. A mutiny by the Bengali officers of Pakistan Air Force (PAF) was started at Tejgaon airbase in East Pakistan.

While the scenario was heated up in the two parts of Pakistan, the traffic density of telecommunication conversation between them started to change. Most of the commercial and trade conversations on the normal and the administrative R/T channels were replaced by political and military conversations. The channels which used to be opened by them for testing only, were now being switched-on and used more frequently and for longer time. ( At WEU,we had made a list of these frequencies under the heading STRATEGIC FREQUENCIES, and were sure that these were going to be used for important conversations). Our Ops room started buzzing with activities. My responsibilities also became very stringent. We had to ensure that, while no intelligence of relevance should go unreported to the higher command, they should not be burdened with irrelevant reporting. All the officers and men at the WEU rose to the occasion. We had also to be vigilant against the fifth columnists, especially after one of our own uniformed NCO was detained by military policemen. Our OC who was very knowledgeable, kept on giving pep talks to all of us. Quite often, he would invite specialists to talk about the various types of warfare. This kept our staff always on the alert.

We kept on passing details of various intercepted intelligence information to our Directorate and were told that some of the intelligence intercepted by us had been very important and useful. The density of telephone traffic remained very high After the Bengali PAF officers mutinied, our interceptions became very useful and the density of our purposeful reporting also increased further. Since our monitoring was on 24×7 basis, many a times I and many others had to spend most of the 24 hours in the Unit only. We reported that Iran was rushing its Boeing and C-130s for carryinging Pakistani army personnel to East Pakistan much earlier than other Intelligence organizations of the country. Similarly, we reported that though China was ready to help Pakistan military, they did not agree to put pressure on India by moving their army to occupy Indian territory. The incidence of firing on the Allouette Helicopter in which the Pakistani army officer Maj. Gen. Khadim Raja was travelling, was also reported by us, immediately after the incidence . 


The Pakistani military spokesmen also were trying to play psychological warfare on our men operating the channels through these very communication channels. They were sure that their R/T channels were being intercepted by Indians. Therefore, many times they used to pass on irrelevant or wrong information on their channels to mislead us. We had to guard our R/T operators through regular pep talks to keep their morale high and to differentiate between right & wrong information.

When Yahya imposed martial law in East Pakistan and appointed Lt. Gen. Tikka Khan as the administrator, the Pakistani channels started encrypting most of their military conversations. The decoding cards available were used extensively after the declaration of martial law. A very large exodus of Bengali Muslims as well as other Bengali Hindus were reported by our Unit. 

It was 14 December,1971 when one of our R/T Operators, Corporal B P Singh brought a log to me at about 1045 hrs., which mentioned about a conversation between some Dhaka Governor House official and a West Pakistan government official. I thought it to be one of the routine official conversations. However, when Cpl. Singh told me that the conversation was encrypted and he had to use one of the decoding cards to listen and record the English conversation, it evinced my interest. On checking the log book, I further found that the conversation was intercepted on one of the strategic frequencies. I asked for the audio recording of the conversation. It mentioned about some meeting in the Government House to be held the same evening, which was to be chaired by the Dhaka Governor himself. As I listened further, I found it revealing the names of the officials attending this meeting. The names included those of General Tikka Khan and the Martial Law Administrator, AOC, PAF Dhaka among others. I heard and re-heard the recording many times and asked the operator to type out the same.

Unfortunately, our OC, Squadron Leader Kapoor was not available for advice, since he had to go on compassionate leave to attend on his mother who was dangerously ill at Lucknow. After making sure that what I heard was of importance, specially because the war of 1971 was critically placed, I rang up the ADSI (Air) on the dedicated phone and informed him about the particular intercept at about 1250 hrs. the same day.After about one hour, Wing Commander Bannerjee rang me back and asked me if the conversation has been audio taped. On my confirmation, he asked me to personally carry it to the Directorate. The rest is history. The intercept intelligence that General Jacob mentioned in his article, is this very intercept on the basis of which Dhaka Governor House was bombed  (More!) and Pakistan military surrendered to the Indian Forces on 16 December, 1971.

When I heard that our intercept was the basis of bombing Dhaka Governor House ,which proved to be the death- knell for the Pakistani Force , I congratulated myself for my decision taken in December 1962 to decline the USA post-doctoral Fellowship and serve the country proactively. I thanked the Almighty for my decision of not proceeding to USA but to join the Indian Air Force.

Subsequently, I wrote a citation for Cpl. B P Singh and recommended him for an award. I was happy when he was awarded the Vishisht Sewa Medal (VSM) for the devotion to his duty.

The author is Editor, “EAGLES’ EYE”, Indian Air Force Association

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