Dive Brief:

• Retailers are unleashing another round of discounts and shipping deals on Monday, traditionally one of the biggest online sales days of the season. Walmart announced a slew of perks, including its largest assortment ever available for same-day pickup and available until 6 p.m. Christmas Eve, the retail giant said in an email to Retail Dive. Target also announced "Green Monday" savings that went as high as $25 off every $100 spent.

• "Green Monday" was coined by eBay 10 years ago, referring to the online marketplace's biggest holiday sales day at the time — the second Monday in December. This year the marketplace, which has been touting its price-match guarantee, announced massive discounts on items like Bose sound systems, David Yurman jewelry and Dyson hair dryers, with more to come, according to an email to Retail Dive. 

• Green Monday arrives as imports at major retail ports are estimated to rise 1.5% this month over the same time last year and rise 6.4% for the year, according to the monthly Global Port Tracker report released Friday by the National Retail Federation and Hackett Associates. Jonathan Gold​, NRF vice president for supply chain, said the numbers show that "retailers are doing last-minute restocking as consumers head toward the finish line of the shopping season."

Dive Insight:

Walmart’s latest salvo in the holiday sales wars represents both its efforts to become a more aggressive player online as well as recent moves to nudge online customers to its stores.

It comes amid a holiday period buoyed so far by a healthy economy, brisk consumer confidence and cooperative weather. 

It also comes as the largest traditional retailers are taking Amazon more seriously as a competitor. The upgrades and discounts are a boon for customers, but they have also sparked concerns about a damaging price war. 

Walmart, Target and others have been investing feverishly in technology, shipping offerings and price so that they aren’t left behind. And it's not just talk. New research has shown Walmart tracking ever closer to Amazon in online pricing. 

In November, Walmart said it would triple its online assortment and roll back prices on thousands of top gifts, with more than 400 rollbacks on toys alone. It has also maintained free two-day shipping on online purchases over $35 and discounts on select items purchased online and picked up in stores. Such moves don’t happen in a vacuum, of course. When Amazon announced its two-day shipping deal, Amazon followed suit.

And that, of course, puts pressure on everyone else to offer free shipping. And it creates the expectation among consumers that they should receive the perk, which pressures not only margins but the package carriers, as they grapple with the largest online sales volume in history. UPS last week warned of delays in package delivery, despite steps to beef up its operations for the holiday season.

This story is part of our ongoing coverage of the 2017 holiday shopping season. You can browse our holiday page and sign up for our holiday newsletter for more stories.