Boxer Oscar de la Hoya hosts “The Mexican-American War” (7 p.m., History). Combining interviews, archival illustrations and dramatic re-creations, “War” offers a detailed and often surprising account of the bloody conflict.

Believing America had a divine right to Mexican territory north of the Rio Grande River, President James K. Polk in 1846 offered $30 million for territories that stretched from Texas to California and north to Wyoming. Rather than prevent war, this offer insulted the Mexican government. Both sides sent troops to their contested border and war ensued.

“War” looks at the conflict from both sides and explains how the war turned out to be much longer and bloodier than Polk imagined. More than 30 percent of American forces would die, many from disease. Future president Ulysses S. Grant saw his first military action in Mexico, as did Robert E. Lee. Citing memoirs and contemporary accounts, “War” makes the case that both Grant and commander and future president Zachary Taylor had major qualms about the legitimacy of the war.

¢ The acclaimed Canadian high school drama “Degrassi” (7 p.m., The N) enters its sixth season of heartache, college prep and a multitude of valuable lessons.

“Degrassi” is followed by the second-season debut of “South of Nowhere” (8 p.m., The N).

¢ Caterer, chef, cookbook author and feisty Southern charmer Paula Deen takes on prime time with “Paula’s Party” (9 p.m., Food). Deen entertains a studio audience with recipes and anecdotes about her life and loves on this weekly series, debuting tonight with a look at dishes that put folks in the mood for love. Or, as Deen puts it, food that make you “romantic-al.”

Tonight’s other highlights

¢ Camryn Manheim joins the cast of “Ghost Whisperer” (7 p.m., CBS).

¢ Scheduled on “Dateline” (8 p.m., NBC): Petaluma, Calif., predators.

¢ A champion emerges on “Celebrity Duets” (8 p.m., Fox).

¢ A disturbed woman takes Megan hostage on “Numb3rs” (9 p.m., CBS).

¢ The photo of a murder victim sparks a sharp response on the Internet on “Law & Order” (9 p.m., NBC).

¢ Scheduled on “20/20” (9 p.m., ABC): the female brain.

¢ Fishermen angle to find out where they’re biting on “Off the Hook” (9 p.m., Versus, formerly OLN).