The Nigerian Army (NA) the largest components of Nigerian Armed Forces, with 100,000 professional personnel.  The original elements of the Royal West African Frontier Force (RWAFF) in Nigeria were formed in 1900.
During the Second World War, British-trained Nigerian troops saw action with the 1st (West Africa) Infantry Brigade, the 81st and the 82nd (West Africa) Divisions which fought in the East African Campaign (World War II) and in the Far East.
In Nigeria, from a force of 18,000 in infantry battalions and supporting units, strength rose to around 126,000 in three divisions by the end of the Nigerian Civil War in 1967.  In terms of doctrine, the task of the Federal Nigerian army did not fundamentally change: its task remained to close with and defeat an organised enemy.
The rapid expansion saw a severe decline in troop quality. The Nigerian expansion process led to an extreme shortage of commissioned officers, with newly created lieutenant-colonels commanding brigades, and platoons and companies often commanded by sergeants and warrant officers. This resulted in tentative command-and-control and in rudimentary staff work.  One result of the weak direction was that the Federals’ three divisions fought independently, and competed for men and materiel. Writing in a 1984 study, Major Michael Stafford of the US Marine Corps noted that «Inexperienced, poorly trained and ineptly led soldiers manifested their lack of professionalism and indiscipline by massacres of innocent civilians and a failure to effectively execute infantry tactics.»  Among the results was the 1967 Asaba massacre.
The influence of individual personalities are generally greater in the armies of developing states, as they tend to have weaker institutional frameworks. Key personalities involved in Nigeria included then-Colonel Olusegun Obasanjo. Obasanjo is particularly important due to his efforts to reorganise his command, 3 Division, during the civil war to improve its logistics and administration. The reorganisation he instituted made the Division capable of carrying out the offensive that ended the civil war.
The Nigerian Army fought the civil war significantly under-resourced; Obasanjo’s memoirs chronicle the lack of any stocks of extra equipment for mobilisation, and the «haphazard and unreliable system of procurement and provisioning» which lasted for the entire period of the war.  Arms embargoes imposed by several Western countries made the situation more difficult.
The U.S. intelligence community concluded in November 1970 that «..The Nigerian Civil War ended with relatively little rancor. The Igbos are accepted as fellow citizens in many parts of Nigeria, but not in some areas of former Biafra where they were once dominant. Igboland is an overpopulated, economically depressed area where massive unemployment is likely to continue for many years. 
The U.S. analysts said that «..Nigeria is still very much a tribal society. » where local and tribal alliances count more than «national attachment. General Yakubu Gowon, head of the Federal Military Government (FRG) is the accepted national leader and his popularity has grown since the end of the war. The FMG is neither very efficient nor dynamic, but the recent announcement that it intends to retain power for six more years has generated little opposition so far. The Nigerian Army, vastly expanded during the war, is both the main support to the FMG and the chief threat to it. The troops are poorly trained and disciplined and some of the officers are turning to conspiracies and plotting. We think Gowon will have great difficulty in staying in office through the period which he said is necessary before the turnover of power to civilians. His sudden removal would dim the prospects for Nigerian stability.»