CAPTION: Illustrations 1 through 4, French and Italian designers have enlisted a military look as a major fall theme, but it's nothing new in Washington. Military surplus - current or vintage - has been big here since the 1960s. At first it was an anti-fashion step, but the sturdiness of fabric, reasonable prices, quality of construction as well as classic, functional styling kept it popular . . . Pictured from left a popular year-round jacket in Europe for young men and women is the battle jacket, this one from theBlack Watch of Canada, from Unique Imports, Alexandria, $25 (shirt and skirt from Casual Corner); perfect bathing suit coverup, the olive drab V-neck all cotton T-shirt, best in big sizes, from Annandale Surplus, $2.49 (medals in many ribbon colors from France at Bloomies); high rise aviator pants with pleated front and thigh pocket from Britches Great Outdoors, $21, worn with fine striped cotton camp shirt, also Britches Great Outdoors, $18.50; ghurka drill shorts for men or women in khaki, $10, with band collar shirt, $8.50, both from Classic Clothing. All battle ribbons and star insignia jewelry from A&N Trading Co., by Martha Vaughan for The Washington Post