The new professional head of the Army Sir David Richards took charge today, pledging to focus on the military effort in Afghanistan.
General Richards, the Chief of the General Staff, will also face battles closer to home in order to ensure that his troops have the equipment and support they need.
His outspoken predecessor General Sir Richard Dannatt was frequently at odds with ministers over the issue, and Gen Richards acknowledged he would be a "hard act to follow".
Gen Richards has first-hand experience of the challenge in Afghanistan as a former head of the International Security and Assistance Force.
He said: "As part of the Defence team, I will continue to focus on what is needed to meet the Government's aims in Afghanistan and the region, and ensuring the Army achieves the tasks laid upon it."
Gen Richards added: "The Army's most valuable assets are its people: it is essential that we continue to look after our soldiers and their families, especially those injured or affected adversely through conflict."
One of the main challenges he will face in Whitehall is the upcoming strategic defence review (SDR) as all three services seek to protect their share of the military budget.
All main parties have committed to holding a root and branch review after the next election.
Gen Richards said: "Looking to the longer term, I will be focusing on making sure that the Army is geared up for future conflict as it evolves in this highly interdependent and globalised era."
In his last public speech before standing down, Gen Dannatt pleaded for the SDR to focus on the current campaign in Afghanistan.
He said: "We must have what we absolutely need for the short-term and limit our ambitions for the medium and the long-term to what we can afford."
Gen Dannatt was unrepentant about his high-profile campaign to secure more equipment for his troops amid allegations that he had been "politicised".
He has admitted "waging some kind of campaign within the Ministry of Defence and within Government" to make sure commanders on the front line have got the right level of troops and kit.
But Gen Richards, asked earlier this month if he would be presenting a "shopping list" for military equipment on his first day in office, answered: "I will not."
Gen Dannatt's departure from the Army is unlikely to mean that ministers have heard the last from him.
He now takes up the post of chairman of the Royal United Services Institute think-tank - a perfect platform from which to expound his views, unfettered by any last constraints of office.
He also becomes the 159th Constable of the Tower of London, a ceremonial role dating back to the 11th century.
In a farewell message to his troops, Gen Dannatt said: "It has been a tremendous honour and privilege and a deeply humbling experience to lead you all for the past few years - you are truly outstanding people.
"As I march into the military sunset I do so confident that the Army's determination, professionalism and reputation remains where it should be: second to none."
Liberal Democrat defence spokesman Nick Harvey said: "General Richards has a formidable reputation.
"But he faces massive challenges over equipment shortages, failing welfare policy and the need for a clear strategy in Afghanistan.
"His predecessor, General Dannatt, was right to champion the needs of our troops.
"Gordon Brown must use General Richards' appointment as an opportunity to get a grip on Britain's defence policy and give our troops the backing they deserve."