The M1 Abrams tank has survived the Cold War, two conflicts in Iraq and a decade of war in Afghanistan. No wonder – it weighs as much as nine elephants and is fitted with a cannon capable of turning a building to rubble from two and a half miles away.

But now the machine finds itself a target in an unusual battle between the Defense Department and lawmakers who are the beneficiaries of large donations by its manufacturer.

The Pentagon, facing smaller budgets and looking towards a new global strategy, has decided it wants to save as much as $3 billion by freezing refurbishment of the M1 from 2014 to 2017, so it can redesign the hulking, clanking vehicle from top to bottom.

Its proposal would idle a large factory in Lima, Ohio, as well as halt work at dozens of subcontractors in Pennsylvania, Michigan and other states.

Opposing the Pentagon’s plans is Abrams manufacturer General Dynamics, a nationwide employer that has pumped millions of dollars into congressional elections over the last decade. The tank’s supporters on Capitol Hill say they are desperate to save jobs in their districts and concerned about undermining America’s military capability.

So far, the contractor is winning the battle, after a well-organized campaign of lobbying and political donations involving the lawmakers on four key committees that will decide the tanks’ fate, according to an analysis of spending and lobbying records by the Center for Public Integrity.

Sharp spikes in the company’s donations – including a two-week period in 2011 when its employees and political action committee sent the lawmakers checks for their campaigns totaling nearly $50,000 – roughly coincided with five legislative milestones for the Abrams, including committee hearings and votes and the defense bill’s final passage last year.

After putting the tank money back in the budget then, both the House and Senate Armed Services Committees have again authorized it this year — $181 million in the House and $91 million in the Senate. If the company and its supporters prevail, the Army will refurbish what Army Chief of Staff Ray Odierno described in a February hearing as “280 tanks that we simply do not need.”

It already has more than 2,300 M1’s deployed with U.S. forces around the world and roughly 3,000 more sitting idle in long rows outdoors at a remote military base in California’s Sierra mountains.

The $3 billion at stake in this fight is not a large sum in Pentagon terms – it’s roughly what the building spends every 82 minutes. But the fight over the Abrams’ future, still unfolding, illuminates the major pressures that drive the current defense spending debate.

These include a Pentagon looking to free itself from legacy projects and modernize some of its combat strategy, a Congress looking to defend pet projects and a well-financed and politically savvy defense industry with deep ties to both, fighting tooth-and-nail to fend off even small reductions in the budget now devoted to the military – a total figure that presently composes about half of all discretionary spending.