“Improvise, adapt, (and) overcome” has become an unofficial motto of the United States Marine Corps and has also been used in business and in government. Clint Eastwood said these lines in the military film Heartbreak Ridge (1986):
 
“You’re Marines now. You adapt. You overcome. You improvise. Let’s move. Four minutes!”
 
There is no documentary evidence—such as printed evidence in Leatherneck—Magazine of the Marines—that “improvise, adapt, overcome” (usually in that order, or as “adapt, improvise, overcome” with “overcome” last) was in use before the movie’s 1986 release. Some have claimed, however, that similar words were spoken by Marines well before 1986. 
 
     
Wikipedia: Culture of the United States Marine Corps
The Culture of the United States Marine Corps is widely varied, but unique amongst the branches of the United States armed forces. Because its members are drawn from across the United States (and resident aliens from other nations), it is as varied as each individual Marine, but tied together with core values and traditions passed from generation to generation of Marines. As in any military organization, the official and unofficial traditions of the Marine Corps serve to reinforce camaraderie and set the service apart from others. The Corps’ embracement of its rich culture and history is cited as a reason for its high esprit de corps.
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Mottos and battle cries
Improvise, Adapt and Overcome has become an adopted mantra in many units.
 
Unofficial, Unabridged Dictionary for Marines
Improvise, Adapt and Overcome
An unofficial mantra of the Marine Corps based on the fact that the Corps generally received Army hand-me-downs and the troops were poorly equipped. Despite this, the Marine Corps has been successful mostly because of the creativity of its people and their success-based attitude.
   
The Internet Movie Database 
Memorable quotes for
Heartbreak Ridge (1986)
Highway: Drop your cocks and grab your socks! Off your ass and on your feet. Let’s move. Knees to the breeze in 5 minutes.
Profile: It’s Goddam 5 o’clock. You said six!
Highway: So I lied. So I can’t tell time. So maybe some communist bastard’s going to make an appointment pop you a new asshole in your forehead. You’re Marines now. You adapt. You overcome. You improvise. Let’s move. Four minutes!
   
8 December 1986, Orlando (FL) Sentinel, “Ho-hum ‘Heartbreak’ is ultimate Eastwood” by Jay Boyar, pg. C1:
“Improvise, overcome and adapt,” is Highway’s motto, a code that puts him constantly at odds with his by-the-book commander.
 
29 February 1988, Rockford (IL) Register Star, “Cubs getting acquainted with Zimmer’s new style” by Jerry Bonkowski, pg. 3C, col. 3:
In effect, he’s adopted as part of his managerial philosophy one of the Marines’ slogans: “Improvise, overcome and adapt.”
 
9 April 1988, New Orleans (LA) Times-Picayune, “Jack Clark prepping for return to N.Y.” by Tom Verducci, pg. D8, col. 6:
“It’s like Clint Eastwood said, ‘You’ve got to improvise, adapt and overcome,’” Clark said by telephone from Florida.
 
24 January 1989, Marietta (GA) Daily Journal, “Sutton finding ways to keep ‘Cats scratching,” pg. 3C, col. 1:
The new rage with Kentucky players became adapt, improvise and overcome.
   
OCLC WorldCat record
SPECIAL SECTION: CATHOLIC HEALTH CARE IN RURAL AMERICA - “Adapt, Improvise, Overcome!” - The staff of a small rural hospital that has many Medicare-age patients finds the U.S. Marines’ motto to be extremely relevant.
Author: Robert A Dockter
Publisher: St. Louis : Catholic Health Association of the United States, 1984-
Edition/Format:  Article : English
Publication: Health progress. 85, no. 2, (2004): 31
Database: ArticleFirst
Other Databases: British Library Serials
 
Google Books
The Marine Corps Way:
Using maneuver warfare to lead a winning organization
By Jason A. Santamaria, Vincent Martino and Eric K. Clemons
New York, NY: McGraw-Hill
2004
Pg. 149:
Another common maxim in the Marine Corps is “Improvise, Adapt, Overcome.” Long before Hollywood popularized it, Marines used the phrase to reflect their preference for being a fluid, loosely reined force that could spontaneously react to rapidly changing situations, rather than a rigid outfit that moved in a specific direction with a precise plan.
 
Google Books
Title Improvise. Adapt. Overcome.: More Ideas for Advancing Your Business
Authors Kenneth Keller, W., Kenneth W. Keller
Publisher Authorhouse, 2006
ISBN 1425948014, 9781425948016
Length 144 pages
Subjects Business & Economics › Careers › General
 
OCLC WorldCat record
Improvise, Adapt, and Overcome
Publisher: Easton, Pa. : Section of Chemical Education, American Chemical Society, [1924-
Edition/Format:  Article : English
Publication: Journal of chemical education. 85, no. 1, (January 2008): 13
Database: ArticleFirst
   
YouTube
HeartBreak
Uploaded by aGreekJoy on Jun 27, 2009
Improvise, adapt, overcome
     
ScrippsNews
Improvise, adapt, overcome in the great outdoors
Submitted by SHNS on Fri, 01/06/2012 - 13:20
By TERRY TOMLIN, Tampa Bay Times
(...)
I woke up dreaming about Clint Eastwood. Actually, I had been dreaming about one of his movies, “Heartbreak Ridge.” In the film Eastwood’s character, a U.S. Marine gunnery sergeant, tells his squad members that they must “improvise, adapt and overcome.”
 
The movie star did not coin the phrase. It is the unofficial mantra of the Corps, the smallest and most poorly funded branch of the military. As a result, Marines are accustomed to doing more with less.