2015 Women's World Cup: 5 Storylines to Follow Ahead of US-Germany Semifinal

— -- The United States soccer team takes on top-ranked Germany tonight in the semifinals of the Women's World Cup at Montreal's Olympic Stadium -- putting it just one step away from Sunday's final.

The U.S., ranked No. 2 in the world, is looking to win its first World Cup since 1999. Germany, on the other hand, last won the World Cup in 2007. Both the United States and Germany have each won two world titles.

Ahead of the game, here are five storylines to follow:

1. U.S. defense and Hope Solo have been unbeatable

In five matches the U.S. has played at the World Cup this year, the team has only allowed one goal. That was against Australia on June 8, which ended with the U.S. victorious by 3-1. ESPN commentator and former U.S. star Julie Foudy said that Solo and "rock-solid defense will be what the U.S. women ride to victory."

2. Waiting on Abby Wambach

Two-time Olympic gold medalist Abby Wambach, 35, was the 2012 FIFA World Player of the Year. She's a veteran of the U.S. team since 2001. A World Cup title is the only thing missing from her resume. It remains to be seen whether she can contribute further in a meaningful way in tonight's game.

Called "the heir" to Mia Hamm by ESPN, Wambach may or may not play in next summer's Olympics in Brazil. Wambach surpassed Hamm as the world's all-time leading goal scorer for men and women on June 20, 2013. She currently has 183 goals in 247 national team appearances. The oldest (and most capped player), however, on the U.S. team is defender Christie Rampone, 40, who has amassed 307 international appearances.

3. Will Alex Morgan be fit enough to play 90 minutes?

With a bone bruise on her left knee from April, U.S. forward Alex Morgan, 25, entered this year's World Cup on the bench before joining the match against Australia as a late sub.

Morgan hopes she will have more to her legacy than the the one goal she scored at this tournament. The striker will turn 26 on Thursday. It remains to be seen if she can play another full 90 minutes against the physically tough Germans.

4. How did Germany get so good?

The Germans are the best team in women's soccer and currently ranked No. 1 in the world by FIFA. Germany is considered by many to be a favorite to reach the championship game, according to odds from FiveThirtyEight. With German striker Celia Sasic leading the tournament with six goals, it's not hard to believe. While the strength of the U.S. may be its defense, the Germans score with their winning offense.

The U.S. has met Germany three previous times at a Women's World Cup. The last time they met in the tournament was the 2003 semifinals, when Team USA lost. Their most recent match up was April 5, 2013, in a game that ended 3-3.

5. Can US fans create a home-field advantage?

With only a country border away from the U.S., Montreal could be inundated with an abundance of American fans.

"It’s a World Cup with a little bit of a difference,” Morgan told FIFA.com. “There have been so many USA fans at the last few games that it’s felt like we’ve been playing at home, even though we’re in Canada. We have a lot of support and our families come to see us more often."

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