Everything old is new again for the U.S. Marine Corps.

Four years ago, faced with pressure to cut spending and a looming threat of "sequester," the Pentagon canceled a controversial project to spend billions of dollars buying new "Expeditionary Fighting Vehicles" for the Marine Corps. Four years later, though, the Corps plans to open a new round of bidding to build a completely different amphibious tank.

A little bit of history

Designed to be launched from amphibious assault ships miles offshore, to sail those miles like a boat, then assault a beach and move inland on tracks like a tank, General Dynamics' (NYSE:GD) EFV was a true marvel of engineering. Unfortunately, as then-Marine Corps Commandant Gen. James Amos lamented, the $15.5 billion price tag to build the things failed to meet "reasonable affordability criteria."

Result: The Marine Corps cut bait on the $3 billion already invested in EFV development, and killed the program outright.

Last week, though, USNI News reported the Marines will soon issue a request for proposals from defense industry companies to build a new vehicle for moving Marines from ship to shore. Dubbed "Amphibious Combat Vehicle 1.1," or ACV 1.1, this less ambitious project aims to build a 35-ton armored beast that can:

Launch from an amphibious assault ship 12 miles offshore, carrying about a dozen Marines.

Traverse those miles of choppy ocean at a speed of at least 8 knots.

Then roll up the shore and assault defending troops with its M2 .50-caliber machine gun and Mark 19 automatic grenade launcher, functioning as an armored personnel carrier.

What will it cost?

In contrast to the EFV, the unit cost on which had surged past $22 million (twice the cost of an M1 Abrams tank) by the time the program was canceled, ACV is expected to be significantly more affordable (if not exactly cheap). Current best guesses put the ACV's "1.1" iteration at roughly $4.5 million per unit, with a planned upgrade to a faster, more robust version "2.0" craft costing perhaps $12 million to $14 million each.

Numbers are in flux, but anywhere from 573to perhaps 694 ACV 1.1 and 1.2 craft could eventually be built, followed by more units of the planned 2.0 version. This suggests a total program cost of $2.6 billion to $3.1 billion -- or more. If all goes as planned, ACVs could begin operational service by 2020.

Who gets the loot?

At least four separate defense contractors are expected to bid on the work: General Dynamics (again), along with Lockheed Martin (NYSE:LMT), SAIC (NYSE: SAI), and BAE Systems (OTC:BAES.Y). These companies will compete to win one of two contracts on offer to provide prototype ACVs for the Marines to test out.

Which will win? As the incumbent manufacturer of the 1970s-era Assault Amphibious Vehicles that ACV will replace, BAE Systems probably has pole position in this race. But as the company that won the last big competition to build the Marines a new amphibious assault tank (i.e., the late, lamented EFV), General Dynamics probably has the best "feel" for what the Marines will be looking for in the ACV -- and accordingly a good chance of meeting those needs.

Lockheed Martin and SAIC probably have the weakest chances -- although neither can be counted out. Indeed, as you can see in the photos above and below, Lockheed Martin already has a prototype ACV built and ready to go.